How to Get Random Permutation of Integers in Golang?

Go language provides inbuilt support for generating random numbers of the specified type with the help of a math/rand package. This package implements pseudo-random number generators. These random numbers are generated by a source and this source produces a deterministic sequence of values whenever the program run. And if you want to random numbers for security-sensitive work, then use the crypto/rand package.

You are allowed to generate a slice of n ints which contains a non-negative pseudo-random permutation of the integers [0, n) from the default source with the help of the Perm() Function provided by the math/rand package. So, you need to add a math/rand package in your program with the help of the import keyword to access the Perm() function.

Syntax:

func Perm(n int) []int

Let us discuss this concept with the help of the given examples:

Example 1:

// Golang program to illustrate
// how to get a random number
package main

import (
    "fmt"
    "math/rand"
)

// Main function
func main() {

    // Getting the random permutation
    // of integers in the form of slice
    // Using Perm() function
    for _, res_1 := range rand.Perm(4) {

        // Displaying the result
        fmt.Println("Slice 1 Element: ", res_1)
    }
    for _, res_2 := range rand.Perm(3) {

        // Displaying the result
        fmt.Println("Slice 2 Element: ", res_2)
    }

}

Output:

Slice 1 Element:  0
Slice 1 Element:  1
Slice 1 Element:  2
Slice 1 Element:  3
Slice 2 Element:  1
Slice 2 Element:  2
Slice 2 Element:  0

Example 2:

// Golang program to illustrate
// how to get a random permutation
// of integers
package main

import (
    "fmt"
    "math/rand"
)

// Main function
func main() {

    // Getting the random permutation
    // of integers in the form of slice
    // Using Perm() function
    res_1 := rand.Perm(5)
    res_2 := rand.Perm(7)
    fmt.Println("Slice 1: ", res_1)

    // Finding the length of the slice
    fmt.Println("Length of Slice 1: ", len(res_1))

    // Finding the capacity of the slice
    fmt.Println("Capacity of Slice 1: ", cap(res_1))

    fmt.Println("Slice 2: ", res_2)

    // Finding the length of the slice
    fmt.Println("Length of Slice 2: ", len(res_2))

    // Finding the capacity of the slice
    fmt.Println("Capacity of Slice 2: ", cap(res_2))

}

Output:

Slice 1:  [0 4 2 3 1]
Length of Slice 1:  5
Capacity of Slice 1:  5
Slice 2:  [4 1 5 0 3 2 6]
Length of Slice 2:  7
Capacity of Slice 2:  7