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Golang has packages like os, io, and Archie/zip that can be used to read and print all the files from a zipped file. A zip file is a compressed collection of a set of files/folders. The OS package is used for performing copy operations, the io pacakge is for reading and writing operations whereas the archive/zip package is for unzipping and zipping the file. In this article, we are going to learn about using all these packages to perform the copy and unzipping of the files and printing the same.

Method 1: Using io and os package

This program uses the archive/zip package to read a zip file’s contents. It opens the zip file using the zip.OpenReader function, which returns a zip.ReadCloser type. Then, it uses a range loop to cycle over all of the files in the archive, uses the Open method to open each file, and print the file name and contents to the standard output.

Syntax zip.OpenReader

This function belongs to the archive/zip package. The primary focus of this function is to open and read the contents of a zip file. It takes only one input i.e. the zip file.

Algorithm

Step 1 − Create a package main and declare fmt(format package), os and io package in the program where main produces executable codes and fmt helps in formatting input and output.

Step 2 − Use the zip to open the zip file in the main menu. Use the OpenReader function, then put the output in the variable read. Print the error message and then retry if a problem exists. So that it closes automatically when the function completes, defer the Close method on read.

Step 3 − Use a range loop and the chúng tôi field to iterate through the files in the zip package.

Step 4 − Then, Use the Open method to open the current file at each iteration, then save the outcome to the variable v. Print the error message and then retry if a problem exists.

Step 5 − To ensure that v is automatically closed after the loop is finished, use the close statement and defer keyword on v.

Step 6 − Print the filename using printf, using the Name field of the chúng tôi type, and chúng tôi to copy the contents of v to the output.

Step 7 − If an error comes while printing the file name, print the error on the console.

Example

In this example, we will use io and os package functions to execute the program.

package main import ( "archive/zip" "fmt" "io" "os" ) func main() { read, err := zip.OpenReader("folder.zip") if err != nil { fmt.Println(err) return } defer read.Close() for _, f := range chúng tôi { v, err := f.Open() if err != nil { fmt.Println(err) return } defer v.Close() fmt.Printf("File Name: %sn", f.Name) _, err = io.Copy(os.Stdout, v) if err != nil { fmt.Println(err) return } fmt.Println() } } Output File1.txt File2.txt Method 2: Using archive/zip and io/ioutil package Syntax ioutil.ReadAll

This function belongs to the ioutil package. The main motive to use it is to read the contents of a file into a byte slice. It takes the filename as an input.

Algorithm

Step 1 − Create a package main and declare fmt(format package), archice/zip and io/ioutil package in the program where main produces executable codes and fmt helps in formatting input and output.

Step 2 − Use the zip to open the zip file in the main menu. Use the OpenReader function, then put the output in the variable read. Print the error message and then retry if a problem exists so that it closes automatically when the function completes, defer the Close method on read.

Step 3 − Use a range loop and the chúng tôi field to iterate through the files in the zip package.

Step 4 − Use the Open method to open the current file at each iteration, then save the outcome to the variable v. Print the error message and then retry if a problem exists.

Step 5 − To ensure that v is automatically closed after the loop is finished, postpone the Close function on v.

Step 6 − Use the ioutil.ReadAll function to read the file’s content and put the output of the into the variable b. If an error exists print it on the console.

Step 7 − Then, print the file name and its contents using printf, using the Name field of the chúng tôi type and print the contents of file stored in slice b.

Example

In this example we will use io/ioutil and archive/zip package to execute the program.

package main import ( "archive/zip" "fmt" "io/ioutil" ) func main() { read, err := zip.OpenReader("sample.zip") if err != nil { fmt.Println(err) return } defer read.Close() for _, f := range chúng tôi { v, err := f.Open() if err != nil { fmt.Println(err) return } defer v.Close() b, err := ioutil.ReadAll(v) if err != nil { fmt.Println(err) return } fmt.Printf("File Name: %sn", f.Name) fmt.Printf("%sn", string(b)) } } Output File1.txt File2.txt Conclusion

We executed the program of reading and printing the files from zip file using two methods. In the first method we used io and os package and in the second method we used archive/zip and io/ioutil package to execute the program.

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Golang Program To Differentiate String Operator And Equals() Method

In the Go programming language, strings are a built-in data type that represents sequences of characters. They are defined using double quotes (“) and can contain any valid Unicode characters. The == operator in Go is used to determine whether two values, including strings, are equal. The == operator determines whether two operands are equal by comparing their values and returning a boolean value. On the other hand, the strings package’s EqualFold() method examines two strings case-insensitively and returns a boolean value indicating whether or not they are equal.

Method 1: Using bytes.Equal() method

In this example we will see how to differentiate the string== operator and equals() method. Here, the functions []byte(mystr1) and []byte(mystr2) translate the strings into slices of bytes and then back to bytes. The equal() function compares the two slices and produces a true or false boolean value. It’s crucial to note that since this method compares the bytes representation of the strings, the outcome could vary based on the string’s encoding compared to using the “==” operator.

Syntax bytes.Equal()

In this method two slices of bytes are compared for equality using the equal method. If the slices are equal or not, a Boolean value is returned. The bytes package contains the method’s definition.

Algorithm

Step 1 − Create a package main and declare fmt(format package) and bytes package in the program where main produces executable Examples and fmt helps in formatting input and output.

Step 2 − Create a main function and in that function create a string named mystr1 and mystr2. Print them on the console.

Step 3 − Use bytes.Equal method to check whether the slice converted to bytes are equal or not.

Step 4 − This method will return a Boolean value as false or true.

Step 5 − The output will be printed on the console using fmt.Println() function where ln means new line.

Example

In this example, we are going to use byte.Equal() function of golang.

package main import ( "bytes" "fmt" ) func main() { mystr1 := "hello" fmt.Println("The string1 created here is:", mystr1) mystr2 := "alexa" fmt.Println("The string2 created here is:", mystr2) fmt.Println("Are the strings equal?") fmt.Println(bytes.Equal([]byte(mystr1), []byte(mystr2))) } Output The string1 created here is: hello The string2 created here is: alexa Are the strings equal? false Method 2: Using EqualFold method

In this example we will see how to differentiate string == operator and equals method. Here, the second comparison using strings will result in true for the initial comparison using the == operator. True will be returned by EqualFold(). Let’s see through Example and algorithm to get a crystal-clear understanding of the concept.

Syntax strings.EqualFold()

The case of the characters is not taken into account when using the EqualFold function to compare two strings for equality. If the two strings are equal (true), the function returns a Boolean result, else it returns a false value (false).

Algorithm

Step 1 − Create a package main and declare fmt(format package) and strings package in the program where main produces executable Examples and fmt helps in formatting input and output.

Step 2 − Create a function main and in that function declare two string variables, mystr1 and mystr2, and initialize them with some values.

Step 3 − Use the == operator to compare mystr1 and mystr2.

Step 4 − If mystr1 and mystr2 are equal, print “str1 and str2 are equal” to the console. If they are not equal, print “str1 and str2 are not equal”.

Step 5 − Use EqualFold() function to compare str1 and str2 case-insensitively.

Step 6 − If str1 and str2 are equal, print “str1 and str2 are equal” to the console. If they are not equal, print “str1 and str2 are not equal”.

Step 7 − The print statement is executed using fmt.Println() function where ln means new line.

Example

In the following example, we are going to use EqualFold method

package main import ( "fmt" "strings" ) func main() { mystr1 := "create" fmt.Println("The string1 created here is:", mystr1) mystr2 := "craete" fmt.Println("The string2 created here is:", mystr2) fmt.Println("Are the strings equal using == operator?") if mystr1 == mystr2 { fmt.Println("str1 and str2 are equal") } else { fmt.Println("str1 and str2 are not equal") } fmt.Println("Are the strings equal using EqualFold method?") if strings.EqualFold(mystr1, mystr2) { fmt.Println("str1 and str2 are equal") } else { fmt.Println("str1 and str2 are not equal") } } Output The string1 created here is: create The string2 created here is: craete Are the strings equal using == operator? str1 and str2 are not equal Are the strings equal using EqualFold method? str1 and str2 are not equal Conclusion

We executed the program of differentiating the == operator and equals method using two examples. In the first example we used bytes.Equal() method and in the second example we used EqualFold method to execute the program.

Golang Program To Convert List To Set

In this tutorial, we will write a golang program to convert a list to set. A linked list is a structure that is created dynamically it has two elements one to store the value and other to store the address of the next structure. A set is an abstract data type that can store specific values without repeating any of them and without any particular sequence.

Convert a Linked List to a Set

Now let us look at an example to convert the linked list to a set.

Syntax func make([]type, length, capacity) []type

The make function is used to make a slice or map. It takes three arguments one is the slice name and type that we wish to make followed by the length and capacity of the slice. The function then returns the final slice.

Algorithm

Step 1 − First, we need to import the fmt package.

Step 2 − The next step is to create a node. For that we are defining a new structure called node.

Step 3 − Then we need to create a linkedlist struct. It also has two fields one is the pointer variable called head. This variable points to the head node

Step 4 − Then we have initialized two functions one is the initlist() function. This function is defined on the linkedlist struct and returns the address of the linkedlist{}.

Step 5 − The second function is named as prepend and it is used to add a new node element to the linked list and takes a node as an argument.

Step 6 − Once the data is added to the current node of linked list we need to make the next pointer of linked list to point to the next node and increment the length of linked list

Step 7 − Start the main function and create a new linked list named mylist by calling the initlist() function.

Step 8 − After that we have created couple of nodes and stored string values to them.

Step 9 − The next step is to arrange these nodes together to form a linked list for that we are calling prepend() function by passing each node as an argument to the function.

Step 10 − Then we need to create a set. We have named it as newset and it stores data in string format.

Step 11 − The next step is to iterate over the linked list and on each iteration we are extracting value from the linked list and are storing it on the set.

Step 12 − Then we need to make the pointer variable of linked list to point to the next node and repeat this process until we get the nil or null value.

Step 13 − The next step is to print the set for that we are using fmt.Println() function.

Example package main import ( "fmt" ) type node struct { data string next *node } type linkedlist struct { len int head *node } func initList() *linkedlist { return &linkedlist{} } func (l *linkedlist) prepend(n *node) { node := &node{ data: n.data, } if chúng tôi == nil { chúng tôi = node } else { chúng tôi = l.head chúng tôi = node } l.len++ return } func main() { mylist := initList() node1 := &node{data: "Apple"} node2 := &node{data: "mango"} node3 := &node{data: "Banana"} mylist.prepend(node1) mylist.prepend(node2) mylist.prepend(node3) newset := make(map[string]struct{}) for chúng tôi != nil { newset[mylist.head.data] = struct{}{} chúng tôi = mylist.head.next } fmt.Println("The obtained set is:", newset) } Output The obtained set is: map[Banana:{} mango:{} Apple:{}] Conclusion

We have successfully compiled and executed a go language program to covert a linked list to set along with an example.

Javascript Program For Print All Triplets In Sorted Array That Form Ap

AP is the arithmetic progression in which the difference between two consecutive elements is always the same. We will print all the triplet in a sorted array that form AP using three approaches: Naive approach, binary search method and two-pointer approach.

Introduction to Problem

In this problem we are given by a sorted array meaning all the elements are in the increasing form. We have to find the three elements which are part of the array and form an AP. For example −

Given array: 1 5 2 4 3

From the given array we have two triplets: 1 2 3 and 5 4 3 as the difference between the adjacent elements is equal. Also, as it is written that we have to find the triplets only so we will not find any longer sequences.

Let us move to the approaches to find the triplets −

Approach Naive Approach

In this approach we are just moving over the array using a loop and for each iteration we will run another array for the numbers that are greater as compared to our current index. Then we will again implement a nested array inside the first nested array to find the element which can form AP. Let’s see the code −

Example function findAP(arr){ var n = arr.length for(var i = 0; i< n;i++){ for(var j = i+1;j<n;j++){ for(var k = j+1; k < n; k++){ if(arr[j] - arr[i] == arr[k] - arr[j]) { console.log("Triplet is: " + arr[i] + " " + arr[j] + " " + arr[k]); } } } } } arr = [1, 5, 2, 4, 3] findAP(arr)

The time complexity of the above code O(), where N is the size of the array.

The space complexity of the above code O(1), as we are not using any extra space.

Follow Up to Naive Approach

In the previous approach, when we have two elements then we can find the third one as we have the common difference, so to find the third element instead of using linear search we can use the binary search and reduce the time complexity of the above code −

Example var binarySearch = function (arr, x, start, end) { var mid=Math.floor((start + end)/2); if (arr[mid]===x) return true; return binarySearch(arr, x, start, mid-1); else return binarySearch(arr, x, mid+1, end); } function findAP(arr){ var n = arr.length for(var i = 0; i< n;i++){ for(var j = i+1;j<n;j++){ var third = 2*arr[j]-arr[i]; if(binarySearch(arr,third,j+1,n)){ console.log("Triplet is: " + arr[i] + " " + arr[j] + " " + third); } } } } arr = [1, 5, 2, 4, 3] findAP(arr)

The time complexity of the above code O(), where N is the size of the array.

The space complexity of the above code O(1), as we are not using any extra space.

Efficient Approach

In this approach we are going to use two pointers and find the elements which are at the same difference from the current position. Let us see the code −

Example function findAP(arr){ var n = arr.length for(var i = 1; i< n;i++) { var bptr = i-1 var fptr = i+1 if(arr[i] - arr[bptr] == arr[fptr] - arr[i]){ console.log("Triplet is: " + arr[bptr] + " " + arr[i] + " " + arr[fptr]); bptr--; fptr++; } fptr++; } else{ bptr--; } } } } arr = [1, 4, 7, 10, 13, 16] findAP(arr)

The time complexity of the above code is O(N*N) where N is the size of the given array and space complexity of the above approach is the O(1) as we are not using any extra space.

Note − First two methods are efficient for any type of array that is sorted or unsorted, but the last method is only applicable for the sorted arrays and if the array is not sorted we can make it one and still this method will be best among all others.

Conclusion

In this tutorial, we have implemented a JavaScript program to print all the triplets in a given sorted array that form an AP. Ap is the arithmetic progression in which the difference between two consecutive elements is always the same. We have seen three approaches: Naive approach with O(N*N*N) time complexity, binary search method with O(N*N*log(N)) time complexity, and two pointer approach.

Golang Program To Show Scope Of Variables

In this article, we will write Go language programs to show scope of global and local variables using pointer approach. Scope is referred to as the accessibility of the piece of code in the program in particular function.

Scope can be defined in two ways: globally and locally. Global means a variable declared in the main cannot be overwritten by any modification and remains same everywhere whereas local access means when variable is modified inside the function, it can only be used inside the function and its scope remains in that function only.

Using Same Global and Local Variables

In this method, we will write a Golang program to depict the scope of variables using one global variable and one local variable having same name.

Algorithm

Step 1 − Create a package main and declare fmt(format package) package in the program where main produces executable codes and fmt helps in formatting input and Output.

Step 2 − Create a main function and in that function create a global variable name and assign it with value

Step 3 − Print the name set globally on the console

Step 4 − Call the function named change_name and in that function chage the global variable to different name as set before

Step 5 − Print the different name on the console and also the name after the function is called using Println function from the fmt package where ln means new line

Example

The following example will demonstrate how to create a Golang program to show scope of variables using same global and local variables

package main import "fmt" func main() { name := "Veronica" fmt.Println("Name before function call:", name) change_name() fmt.Println("Name after function call:", name) } func change_name() { name := "Virushi" fmt.Println("Name inside function:", name) } Output Name before function call: Veronica Name inside function: Virushi Name after function call: Veronica Using Pointer Approach

In this particular method, we will write a Golang program to show scope of variables using pointers. A variable named a will be created and assigned a value that will be incremented later.

Algorithm

Step 1 − Create a package main and declare fmt(format package) package in the program where main produces executable codes and fmt helps in formatting input and Output

Step 2 − Create a variable named a and assign it value inside the main function

Step 3 − Print the value of a using Println function from the fmt package where ln means new line

Step 4 − Call the function increment in the main with a pointer to the ‘a’ variable

Step 5 − In the function, increment the value a pointed by the pointer with * operator

Step 6 − Print the value inside the function using Println function

Step 7 − Finally, print the value of a after function is called as did in last steps

Example

The following example will show how to create Golang program to show scope of variables using pointer approach

package main import "fmt" func main() { a := 1 fmt.Println("Value of a before the function is called:", a) increment(&a) fmt.Println("Value of a after the function is called:", a) } func increment(ptr *int) { *ptr++ fmt.Println("Value of a inside function:", *ptr) } Output Value of a before the function is called: 1 Value of x inside function: 2 Value of a after the function is called: 2 Using Global Variable Outside the Main Function

In this example, we will write a Golang program to show scope of variables using global variable outside the main function. An external function will be created in which the variables will be manipulated.

Algorithm

Step 1 − Create a package main and declare fmt(format package) package in the program where main produces executable codes and fmt helps in formatting input and Output

Step 2 − Create a global variable and write a string to it

Step 3 − Create a main function in which further create a local variable and assign a string to it

Step 4 − Print the local variable on the console using Println function

Step 5 − In this step, access the global variable in the main function and print the string

Step 6 − Call the function callingFunction() from the main

Step 7 − In this function, create another local variable using the same variable and print it on the console

Step 8 − Again, access the global variable from another function and print its value

Step 9 − Then, change the global variable value and print the updated value on the console

Step 10 − The print statement is executed using Println function from the fmt package where ln means new line

Example

The following example, illustrates Golang program to show scope of variables using global variable outside the main function

package main import "fmt" var global_variable = "I am a global variable" func main() { var local_variable = "I am a local variable" fmt.Println(local_variable) fmt.Println(global_variable) callingFunction() } func callingFunction() { var local_variable = "I am another local variable" fmt.Println(local_variable) fmt.Println(global_variable) global_variable = "I am a new global variable value" fmt.Println(global_variable) } Output I am a local variable I am a global variable I am another local variable I am a global variable I am a new global variable value Conclusion

We compiled and executed the program of showing scope of variables using three examples. In the first example, we created a string variable and used function to show local and global variable differently. In the second example, pointer approach is used i.e. the pointer is passed in the function as an argument pointing to the variable which is to be incremented and in the third example we will use global variable outside the main and access it inside the external function.

Golang Program To Push An Array Into Another Array

In this tutorial, we will write a go language program to push an array to another array. There are many methods for this. The simplest one is to use equality operator. Here, we will see 3 methods via which we can transfer the contents of one array to another in go programming language.

Method 1: Push an Array of Strings to an Empty Array by using Equality Operator

In this method, we will use equality operator to add the contents of one array to another in the main() section of the program. Note that while transferring elements via this method the elements of the new array will be overwritten.

Syntax func append(slice, element_1, element_2…, element_N) []T

The append function is used to add values to an array slice. It takes number of arguments. The first argument is the array to which we wish to add the values followed by the values to add. The function then returns the final slice of array containing all the values.

func make ([] type, size, capacity)

The make function in go language is used to create an array/map it accepts the type of variable to be created, its size, and capacity as arguments and returns the slice that we can store in the variable.

Algorithm

Step 1 − First, we need to import the fmt package.

Step 2 − Now, start the main() function. Inside this function create two arrays of string data type using make() function and store data in one of these arrays

Step 3 − Then, print these arrays on the screen using fmt.Println() function. After that use equality (==) operator to copy the contents of first array to second one.

Step 4 − Once the array is copied then print the new array thus formed on the screen.

Example

Golang program to push an array of strings to an empty array by using equality operator.

package main import "fmt" func main() { array := make([]string, 0, 3) array1 := make([]string, 0, 3) array = append(array, "Apple", "Mango", "Banana") fmt.Println("The first array is:", array) fmt.Println("The second array is:", array1) array1 = array fmt.Println() fmt.Println("The array obtained after copying the contents is:", array1) } Output The first array is: [Apple Mango Banana] The second array is: [] The array obtained after copying the contents is: [Apple Mango Banana] Method 2: Push an Array of Strings to Another Array using Copy() Function

In this method, we will use copy() library function in go to push the contents of one array to another. Copy is an inbuilt function in go present in strings package.

Syntax func copy(dst, str[] type) int

The copy function in go language is used to copy the values of one source array to the destination array and returns the number of elements copied as the result. It takes the two arrays as an argument and this function is present in strings package.

Algorithm

Step 1 − Import the fmt package.

Step 2 − Start the main() function. Inside this function initialize two arrays of string data type and store values to them using append() function.

Step 3 − Now, print both arrays on the screen and use copy function to copy the contents of first array to the second one.

Step 4 − Once the elements are copied store the number of elements copied in a variable called result and print the final array on the screen along with number of elements copied

Example

Golang program to push an array of strings to another array using copy() function

package main import "fmt" func main() { array := make([]string, 0, 3) var array1 []string array = append(array, "Apple", "Mango", "Banana") array1 = append(array1, "pine-apple", "Cherry") fmt.Println("The first array is:", array) fmt.Println("The second array is:", array1) result := copy(array1, array) fmt.Println() fmt.Println("The array obtained after copying the contents is:", array1) fmt.Println("The number of elements copied are:", result) } Output The first array is: [Apple Mango Banana] The second array is: [pine-apple Cherry] The array obtained after copying the contents is: [Apple Mango] The number of elements copied are: 2 Method 3: Push One Array to another using Append() Function

In this method, we will write a go language program to push the elements of one array to another by using the append() function. When we copy the contents of one array to another by using this function, the current elements of the new array are not overwritten.

Algorithm

Step 1 − Import the fmt package.

Step 2 − Start() the main() function and initialize two arrays. Store data in both arrays and print them on the screen using fmt.Println() function.

Step 3 − Then, use the append function to copy the contents of first array to the second one. The first argument to the function is the array to which we wish to copy the values.

Step 4 − once the array contents are copied to the new array, print the new array thus formed on the screen.

Example

Golang program to push one array to another using the append() function.

package main import "fmt" func main() { array := make([]string, 0, 3) var array1 []string array = []string{"Apple", "Mango", "Banana"} array1 = append(array1, "pine-apple", "Cherry") fmt.Println("The first array is:", array) fmt.Println("The second array is:", array1) array1 = append(array1, array...) fmt.Println() fmt.Println("The array obtained after copying the contents is:", array1) } Output The first array is: [Apple Mango Banana] The second array is: [pine-apple Cherry] The array obtained after copying the contents is: [pine-apple Cherry Apple Mango Banana] Conclusion

We have successfully compiled and executed a go language program to copy the contents of one array to another along with examples. We have made three programs here in the first program we are simply using the equality operator to store the values while in second and third examples we have used go library functions to achieve the result.

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