23.03.28 学习

算法基础课补完计划开始

#include <iostream>
#include <cstring>
#include <queue>
using namespace std;

const int N = 1e5 + 10, M = N;
int n, m;
int h[N], e[M], ne[M], idx;
int d[N];

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

void topsort() {
    queue<int> q;
    int top[N], cnt = 0;
    for (int i = 1; i <= n; i ++ ) {
        if (d[i] == 0) {
            q.push(i);
            cnt ++ ;
            top[cnt] = i;
        }
    }
    // bfs,删除每个点的入度找拓扑序
    while (q.size()) {
        auto t = q.front();
        q.pop();
        for (int i = h[t]; i != -1; i = ne[i]) {
            int j = e[i];
            d[j] -- ;
            if (d[j] == 0) {
                q.push(j);
                cnt ++ ;
                top[cnt] = j;
            }
        }
    }
    // 判断
    if (cnt != n) cout << -1 << endl;
    else {
        for (int i = 1; i <= n; i ++ ) cout << top[i] << ' ';
        cout << endl;
    }
}

int main()
{

    cin >> n >> m;
    memset(h, -1, sizeof h);
    while (m -- ) {
        int a, b;
        cin >> a >> b;
        add(a, b);
        d[b] ++ ;
    }

    topsort();

    return 0;
}