permutation sequence of n without repeats (input: 3, output: [012 021 102 120 201 210])

permutate_n.go

package main

import (
	"fmt"
	"sort"
	"strconv"
)

const num_count int = 3

type IntSlice []int

var this_slice IntSlice
var this_strs []string
var this_str string
var sum_count int = 0

func main() {
	this_slice = *sequence_int(num_count)
	permutate(num_count)
	sort.Strings(this_strs)
	fmt.Print("\n")
	fmt.Print(this_strs)
}

func permutate(n int) {
	if n == 0 {
		this_str = ""
		sum_count++
		for _, cell := range this_slice {
			this_str += strconv.Itoa(cell)
		}
		this_strs = append(this_strs, this_str)
		return
	} else {
		for j := 0; j < n; j++ {
			this_slice.swap(j, n-1)
			permutate(n - 1)
			this_slice.swap(j, n-1)
		}
	}
}

func (slice IntSlice) swap(i, j int) {
	slice[i], slice[j] = slice[j], slice[i]
}

func sequence_int(num int) *[]int {
	seq := make([]int, num)
	for i := 0; i < num; i++ {
		seq[i] = i
	}
	return &seq
}