C++ 解法, 执行用时: 35ms, 内存消耗: 1164KB, 提交时间: 2021-08-01

#include <bits/stdc++.h>
 
using namespace std;
const int maxn = 502;
 
int main(){
    int n, m;
    while(scanf("%d%d", &n, &m) != EOF){
        int in[maxn] = {0};
        vector<int> aps[maxn];
        priority_queue<int, vector<int>, greater<int>> q;
        for(int i=0; i<m; i++){
            int a, b;
            scanf("%d%d", &a, &b);
            in[b]++;
            aps[a].push_back(b);
        }
        for(int i=1; i<=n; i++){
            if(in[i] == 0){
                q.push(i);
            }
        }
        int cnt = 0;
        while(! q.empty()){
            int u = q.top();
            q.pop();
            cnt++;
            printf("%d", u);
            if(cnt < n)    printf(" ");
            for(auto v:aps[u]){
                in[v]--;
                if(in[v] == 0)    q.push(v);
            }
        }
        printf("\n");
    }
 
    return 0;
}

C 解法, 执行用时: 35ms, 内存消耗: 1372KB, 提交时间: 2021-08-31

#include <stdio.h>
#include <string.h>
#define N 501
//创建一个度和图
int Indegree[N];
int Graph[N][N];
int main(){
    int n,m;
    int a,b;
    int count;
    while(scanf("%d %d",&n,&m) != EOF){
        //对图和度进行初始化
        memset(Graph,0,sizeof(Graph));
        memset(Indegree,0,sizeof(Indegree));
        count = 0;
        //对度和图进行一个赋值
        for(int i = 0; i < m; i++){
            scanf("%d %d",&a,&b);
            if(Graph[a][b] == 0){
                Graph[a][b] = 1;
                Indegree[b]++;
            }
        }
        //开始循环拓扑
        for(int i = 0; i < n; i++){
            int flag = n + 1;
            for(int j = 1; j <= n; j++){
                if(Indegree[j] == 0){
                    Indegree[j] = -1;
                    flag = j;
                    count++;
                    break;
                }
            }
            if(flag == n + 1)
                return 0;//若一趟查找，没有可拓扑的顶点，直接退出
            if(count == 1){
                printf("%d",flag);
            }
            else{
                printf(" %d",flag);
            }
            for(int k = 1; k <= n; k++){//更新图信息
                if(Graph[flag][k] == 1){
                    Indegree[k]--;
                }
            }
        }
        printf("\n");
    }
    return 0;
}