57 lines
1.6 KiB
C++
57 lines
1.6 KiB
C++
struct edmonds_karp {
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struct edge {
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int to;
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ll cap;
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ll flow;
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pair<int, int> rev;
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int mark;
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};
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vector<vector<edge>> edges;
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edmonds_karp(int n) : edges(n + 1) {}
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void add_edge(int from, int to, ll cap, int mark = 0, int mark_rev = 0) {
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edges[from].push_back({to, cap, 0, make_pair(to, int(edges[to].size())), mark});
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edges[to].push_back({from, 0, 0, make_pair(from, int(edges[from].size() - 1)), mark_rev});
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}
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ll run(int s, int t) {
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int n = edges.size();
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vector<pii> pa_(n + 1);
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ll res = 0;
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while (1) {
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vector<ll> pf(n + 1);
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deque<int> dq;
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dq.emplace_back(s);
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pf[s] = LLONG_MAX;
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while (dq.size()) {
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int v = dq.front(); dq.pop_front();
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for (auto&& [i, ne] : enumerate(edges[v])) {
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if (pf[ne.to] == 0 and ne.cap > ne.flow) {
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pf[ne.to] = min(pf[v], ne.cap - ne.flow);
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pa_[ne.to] = {v, i};
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dq.emplace_back(ne.to);
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}
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}
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if (pf[t] != 0) {
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break;
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}
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}
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if (pf[t] == 0) {
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break;
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}
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int p = t;
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while (pa_[p].first != 0) {
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auto [x, y] = pa_[p];
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edges[x][y].flow += pf[t];
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auto [z, w] = edges[x][y].rev;
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edges[z][w].flow -= pf[t];
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p = x;
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}
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res += pf[t];
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}
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return res;
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}
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};
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