60 lines
1.2 KiB
C++
60 lines
1.2 KiB
C++
#include <bits/stdc++.h>
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using namespace std;
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const int N = 510;
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bool g[N][N]; // 邻接矩阵
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int in[N]; // 入度
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int n, m; // n个顶点，m条边
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// 小顶堆
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priority_queue<int, vector<int>, greater<int>> q;
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/*
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4 3
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1 2
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2 3
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4 3
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1 2 4 3
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*/
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void toposort() {
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// 所有入度为零的节点入队列，是拓扑序的起始节点
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for (int i = 1; i <= n; i++)
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if (in[i] == 0) q.push(i);
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int cnt = 0;
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while (q.size()) {
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int u = q.top();
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q.pop();
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cnt++; // 又一个节点出队列
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// 输出拓扑序
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if (cnt != n)
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cout << u << " ";
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else
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cout << u << endl;
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for (int i = 1; i <= n; i++)
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if (g[u][i]) {
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in[i]--;
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if (!in[i]) q.push(i);
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}
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}
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}
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int main() {
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while (cin >> n >> m) {
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memset(g, 0, sizeof g);
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memset(in, 0, sizeof in);
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while (m--) {
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int x, y;
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cin >> x >> y;
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if (g[x][y]) continue; // 防止重边
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g[x][y] = 1; // 设置有关联关系
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in[y]++; // 入度+1
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}
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toposort(); // 拓扑序
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}
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return 0;
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} |