Full permutation implementation of Golang permutation algorithm problem

In this paper, an example of Golang permutation algorithm is presented. I will share it with you for your reference as follows:

[permutation and combination problem]

1 altogether N trains (0 < N < 10), each train is numbered 1-9, and the train's outbound serial number is required to be output in lexicographical order.

Input:

Including N positive integers (0) < N < 10), which ranges from 1 to 9. The Numbers are separated by Spaces. The first part of the string does not contain Spaces.

Output:

Output the lexicographical train outbound sequence number, each number separated by a space, each output sequence line feed.

Sample input:

1 2 3

Sample output:

1 2 3
1 3 2
2 1 3
2 3 1
3 1 2
3 2 1

Code implementation:

package huawei

import (

    "fmt"

    "sort"

    "strings"

)

func Test7Base() {

    in := "5 2 3"

    result := outOrder(strings.Fields(in))

    dictSort(result)

    s := format(result)

    fmt.Println(s)

}

// The input trainsNums , returns all permutations 

// Such as the input [1 2 3] , the return [123 132 213 231 312 321]

func outOrder(trainsNums []string) []string {

    COUNT := len(trainsNums)

    // check 

    if COUNT == 0 || COUNT > 10 {

        panic("Illegal argument. trainsNums size must between 1 and 9.")

    }

    // If only 1 The number is directly returned 

    if COUNT == 1 {

        return []string{trainsNums[0]}

    }

    // Otherwise, it will be the last 1 Number inserted into all positions in the preceding permutation number (recursion) 

    return insert(outOrder(trainsNums[:COUNT-1]), trainsNums[COUNT-1])

}

func insert(res []string, insertNum string) []string {

    // Save the result slice

    result := make([]string, len(res)*(len(res[0])+1))

    index := 0

    for _, v := range res {

        for i := 0; i < len(v); i++ {

            // in v Each of the 1 Two elements are inserted in front of each other 

            result[index] = v[:i] + insertNum + v[i:]

            index++

        }

        // in v Backmost insertion 

        result[index] = v + insertNum

        index++

    }

    return result

}

// Sort in lexicographical order 

func dictSort(res []string) {

    sort.Strings(res)

}

// Output in the specified format 

func format(res []string) string {

    strs := make([]string, len(res))

    for i := 0; i < len(res); i++ {

        strs[i] = addWhiteSpace(res[i])

    }

    return strings.Join(strs, "\n")

}

// Add a space 

func addWhiteSpace(s string) string {

    var retVal string

    for i := 0; i < len(s); i++ {

        retVal += string(s[i])

        if i != len(s)-1 {

            retVal += " "

        }

    }

    return retVal

}

I hope this article has been helpful to you in the programming of Go language.