package main

import (
  "fmt"
  "strconv"
)

//edge 要求的顺序
var edge map[string]string = map[string]string{
  "2": "5",
  "3": "2",
  "4": "1",
  "1": "3",
}

func main() {
  //结果数组
  var q []string = make([]string, 0)
  //已访问数组
  var visited []string = make([]string, 0)
  for i := 0; i < 5; i++ {
    tupusort(&q, &visited, strconv.Itoa(i))
  }
  // fmt.Printf("visited: %v \n", visited)
  reverse(q)
  fmt.Printf("topusort: %v \n", q)
}

//拓扑排序-DFS
func tupusort(q *[]string, visited *[]string, element string) {
  if !isVisited(visited, element) {
    *visited = append(*visited, element)
    if edge[element] != "" {
      tupusort(q, visited, edge[element])
    }
    *q = append(*q, element)
  }
}

//检查是否存在已访问的数组中
func isVisited(visited *[]string, element string) bool {
  var isVisited bool = false
  for _, item := range *visited {
    if item == element {
      isVisited = true
      break
    }
  }
  return isVisited
}

//反转数组顺序
func reverse(arr []string) {
  for i, j := 0, len(arr)-1; i < j; i, j = i+1, j-1 {
    arr[i], arr[j] = arr[j], arr[i]
  }
}