题目描述

blablabla

样例

import java.util.*;

public class Main{
    static int N = 100010;
    static int[] e = new int[N];
    static int[] ne = new int[N];
    static int[] h = new int[N];
    static int n,idx;
    static int[] d = new int[N];
     static ArrayList<Integer> array = new ArrayList<>(); // 记录点
    static Queue<Integer> q = new LinkedList();
    public static void main(String[] args){
        Scanner sc = new Scanner(System.in);
        n = sc.nextInt();
        int m = sc.nextInt();
        Arrays.fill(h,-1);

        while(m-- > 0){
            int a = sc.nextInt();
            int b = sc.nextInt();
            add(a,b);
        }
        for(int i = 1;i <= n;i++){
            if(d[i] == 0){
                q.offer(i);
                 array.add(i);
            }
        }
        while(!q.isEmpty()){
            int x = q.poll();
            for(int i = h[x];i != -1;i = ne[i]){
                int j = e[i];
                d[j]--;
                if(d[j] == 0){
                    q.offer(j);
                     array.add(j);
                }
            }
        }
        if(array.size() >=  n){
            for(int i = 0;i < n;i++){
                System.out.print(array.get(i) + " ");
            }
        }else{
            System.out.print(-1);
        }

    }
    static void add(int a,int b){
        e[idx] = b;ne[idx] = h[a];h[a] = idx++;
        d[b]++;
    }

}

算法1

(暴力枚举) $O(n^2)$

blablabla

时间复杂度

参考文献

C++ 代码

blablabla

算法2

(暴力枚举) $O(n^2)$

blablabla

时间复杂度

参考文献

C++ 代码

blablabla