mirror of
https://git.sb/baoshuo/OI-codes.git
synced 2024-12-25 17:32:01 +00:00
113 lines
2.3 KiB
C++
113 lines
2.3 KiB
C++
#include <cstdio>
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#include <algorithm>
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#include <cstring>
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#include <queue>
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const int N = 55 << 1,
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M = 50005,
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INF = 1e8;
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int n, m, s, t, flow, max_flow, ans;
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// Graph
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int idx, head[N], edge[M << 1], ver[M << 1], next[M << 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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// Dinic
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int d[N], cur[N];
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bool bfs() {
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memset(d, 0x00, sizeof(d));
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std::queue<int> q;
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q.push(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 (!d[v] && w) {
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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.push(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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int v = ver[i],
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w = edge[i];
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if (d[v] == d[u] + 1 && w) {
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int k = dinic(v, std::min(w, limit - flow));
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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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while (scanf("%d%d", &n, &m) != EOF) {
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idx = 0;
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ans = n;
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memset(head, 0xff, sizeof(head));
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for (int i = 0; i < n; i++) {
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add(i, n + i, 1);
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add(n + i, i, 0);
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}
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for (int i = 0; i < m; i++) {
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int u, v;
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scanf(" (%d,%d)", &u, &v);
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add(u + n, v, INF);
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add(v, u + n, 0);
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add(v + n, u, INF);
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add(u, v + n, 0);
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}
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for (int i = 0; i < n; i++) {
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for (int j = 0; j < i; j++) {
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s = n + i, t = j;
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for (int k = 0; k < idx; k += 2) {
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edge[k] += edge[k ^ 1];
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edge[k ^ 1] = 0;
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}
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max_flow = 0;
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while (bfs()) {
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while (flow = dinic(s, INF)) max_flow += flow;
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}
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ans = std::min(ans, max_flow);
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}
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}
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printf("%d\n", ans);
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}
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return 0;
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}
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