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2234. 多源汇最大流
https://www.acwing.com/problem/content/submission/code_detail/12163019/
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102
AcWing/2234/2234.cpp
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102
AcWing/2234/2234.cpp
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#include <cstring>
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#include <iostream>
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#include <limits>
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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 = 100005,
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M = 1000005;
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int n, m, sc, tc, s, t, 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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std::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 (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.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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std::ios::sync_with_stdio(false);
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memset(head, 0xff, sizeof(head));
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cin >> n >> m >> sc >> tc;
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s = 0, t = n + 1;
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for (int i = 1; i <= sc; i++) {
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int x;
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cin >> x;
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add(s, x, std::numeric_limits<int>::max());
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add(x, s, 0);
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}
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for (int i = 1; i <= tc; i++) {
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int x;
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cin >> x;
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add(x, t, std::numeric_limits<int>::max());
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add(t, x, 0);
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}
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for (int i = 1; i <= m; i++) {
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int u, v, w;
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cin >> u >> v >> w;
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add(u, v, w);
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add(v, u, 0);
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}
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while (bfs()) {
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while (flow = dinic(s, std::numeric_limits<int>::max())) 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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