permutation_num_to_json.go

package main

import (
	"bufio"
	"encoding/json"
	"fmt"
	"os"
	"sort"
	"strconv"
)

const file_path string = "data.json"
const num_count int = 6

type SomeJson struct {
	Slice []int `json:"data"`
}
type IntSlice []int

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

func main() {
	this_slice = *sequence_int(num_count)
	permutate(num_count)
	sort.Ints(this_ints)
	this_json := &SomeJson{Slice: this_ints}
	res_json, err := json.Marshal(this_json)
	if err != nil {
		fmt.Print("error! make json object failed!")
		return
	}
	fmt.Print(string(res_json))
	open_write(string(res_json))
	fmt.Print(len(res_json))
}

func permutate(n int) {
	if n == 0 {
		this_str = ""
		sum_count++
		for _, cell := range this_slice {
			this_str += strconv.Itoa(cell)
		}
		this_int, _ := strconv.Atoi(this_str)
		this_ints = append(this_ints, this_int)
		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 + 1
	}
	return &seq
}

func open_write(data string) {
	if data == "" {
		fmt.Print("error! nothing to write!")
		return
	}
	foi, err := os.OpenFile(file_path, os.O_APPEND|os.O_WRONLY, os.ModePerm)
	if err != nil {
		fmt.Print("error! open file failed!")
		return
	}
	writer := bufio.NewWriter(foi)
	defer foi.Close()
	defer writer.Flush()
	writer.WriteString(data)
}