mirror of
https://git.sb/baoshuo/OI-codes.git
synced 2024-11-09 01:18:47 +00:00
112 lines
1.9 KiB
C++
112 lines
1.9 KiB
C++
#include <iostream>
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#include <algorithm>
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#include <queue>
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using std::cin;
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using std::cout;
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const char endl = '\n';
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const int N = 505,
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M = 5e4 + 5;
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const int INF = 0x3f3f3f3f;
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int n, m, e, s, t, flow, ans;
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int idx, head[N << 1], ver[M << 2], edge[M << 2], next[M << 2];
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int d[N << 1], cur[N << 1];
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void add(int u, int v, int w) {
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next[idx] = head[u];
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ver[idx] = v;
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edge[idx] = w;
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head[u] = idx++;
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}
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bool bfs() {
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std::fill_n(d, N << 1, 0);
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std::queue<int> q;
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q.emplace(s);
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d[s] = 1;
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cur[s] = head[s];
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while (!q.empty()) {
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int u = q.front();
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q.pop();
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for (int i = head[u]; ~i; i = next[i]) {
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int v = ver[i],
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w = edge[i];
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if (w && !d[v]) {
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d[v] = d[u] + 1;
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cur[v] = head[v];
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if (v == t) return true;
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q.emplace(v);
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}
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}
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}
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return false;
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}
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int dinic(int u, int limit) {
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if (u == t) return limit;
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int flow = 0;
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for (int i = cur[u]; ~i && flow < limit; i = next[i]) {
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cur[u] = i;
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int v = ver[i],
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w = edge[i];
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if (w && d[v] == d[u] + 1) {
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int k = dinic(v, std::min(limit - flow, w));
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if (!k) d[v] = 0;
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edge[i] -= k;
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edge[i ^ 1] += k;
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flow += k;
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}
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}
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return flow;
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}
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int main() {
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std::ios::sync_with_stdio(false);
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cin.tie(nullptr);
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std::fill_n(head, N << 1, -1);
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cin >> n >> m >> e;
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s = 0, t = n + m + 1;
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for (int i = 1; i <= n; i++) {
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add(s, i, 1);
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add(i, s, 0);
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}
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for (int i = 1; i <= m; i++) {
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add(n + i, t, 1);
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add(t, n + i, 0);
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}
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for (int i = 1, u, v; i <= e; i++) {
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cin >> u >> v;
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add(u, n + v, 1);
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add(n + v, u, 0);
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}
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while (bfs()) {
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while (flow = dinic(s, INF)) ans += flow;
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}
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cout << ans << endl;
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return 0;
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}
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