60 lines
1.6 KiB
C++
60 lines
1.6 KiB
C++
#include <bits/stdc++.h>
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using namespace std;
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#define int long long
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const int N = 100010, M = N << 1;
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int in[N]; // 入度数组
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// 链式前向星
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int e[M], h[N], idx, w[M], ne[M];
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void add(int a, int b, int c = 0) {
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e[idx] = b, ne[idx] = h[a], w[idx] = c, h[a] = idx++;
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}
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void solve() {
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memset(in, 0, sizeof in); // 入度
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memset(h, -1, sizeof h); // 初始化链式前向星
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idx = 0;
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priority_queue<int> q; // 优先队列大顶堆
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map<pair<int, int>, int> _map; // 使用红黑树保存已经添加过关系的数，防止出现重边
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vector<int> ans;
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int n, m;
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cin >> n >> m; // n个菜，m个关系
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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 (!_map[{x, y}]) { // 防止重复建边
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_map[{x, y}] = 1;
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add(y, x); // 反向建图
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in[x]++; // 记录入度
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}
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}
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// 入度为零的入队列
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for (int i = 1; i <= n; i++)
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if (!in[i]) q.push(i);
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// Topsort
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while (q.size()) {
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int u = q.top(); // 序号大的先出来，然后倒序输出
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q.pop();
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ans.push_back(u); // 记录出队顺序
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for (int i = h[u]; ~i; i = ne[i]) {
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int j = e[i];
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in[j]--;
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if (!in[j]) q.push(j);
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}
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}
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if (ans.size() != n)
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cout << "Impossible!";
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else
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for (int i = n - 1; i >= 0; i--) cout << ans[i] << ' ';
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cout << endl;
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}
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signed main() {
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int T;
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cin >> T;
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while (T--) solve();
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return 0;
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}
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