# Golang : Check if one string(rune) is permutation of another string(rune)

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Problem:

You need to check if a given input string or rune is actually a permutation of another string(rune). For example, you want to test if "hello" and "olleh" is permutation of each other or "你好" and "好你" is permutation of each other.

How to do that?

Solution:

First, check if the lengths of both strings(runes) are the same. If not, then they are not a permutation of each other. Next, sort the letters or characters inside the strings/runes. Compare each character of both sorted results by indexes. If all characters are the same, then they are a permutation of each other.

Here you go!

`````` package main

import (
"fmt"
"sort"
)

type RuneSlice []rune

func (p RuneSlice) Len() int { return len(p) }
func (p RuneSlice) Less(i, j int) bool { return p[i] < p[j] }
func (p RuneSlice) Swap(i, j int) { p[i], p[j] = p[j], p[i] }

func isPermutation(str1, str2 string) bool {
// if lengths are not equal - false
if len(str1) != len(str2) {
return false
}

// sort both strings/runes
var rune1 RuneSlice = []rune(str1)
var rune2 RuneSlice = []rune(str2)

sort.Sort(rune1)
sort.Sort(rune2)

//fmt.Println(string(rune1[:]))
//fmt.Println(string(rune2[:]))

// compare rune1 and rune 2 by indexes
for i := 0; i < len(rune1); i++ {
if rune1[i] != rune2[i] {
return false
}
}

return true
}

func main() {
fmt.Println("test1 and test2 is permutation of each other : ", isPermutation("test1", "test2"))
fmt.Println("hello and olleh is permutation of each other : ", isPermutation("hello", "olleh"))
fmt.Println("你好 and 好你 is permutation of each other : ", isPermutation("你好", "好你"))
}
``````

Output:

test1 and test2 is permutation of each other : false

hello and olleh is permutation of each other : true

Reference:

https://www.socketloop.com/tutorials/golang-sort-and-reverse-sort-a-slice-of-runes

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