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cp-templates/graph/examples/minimum_flow_with_demands.cc

42 lines
1.1 KiB
C++

struct dinic {
// ...
};
void solve() {
read(int, n, m, s, t);
dinic net(n + 1);
int S = 0, T = n + 1;
vector<ll> init(n + 1);
for (int i = 0 ;i < m; ++i) {
read(ll, u, v, lower, upper);
init[v] += lower;
init[u] -= lower;
net.add_edge(u, v, upper - lower);
}
ll sum = 0;
for (int i =1; i <= n; ++i) {
if (init[i] > 0) {
net.add_edge(S, i, init[i]);
sum += init[i];
} else if (init[i] < 0) {
net.add_edge(i, T, -init[i]);
}
}
net.add_edge(t, s, INFLL, 1, 1); // WARN: s->t is wrong
if (sum != net.run(S, T)) {
cout << "please go home to sleep\n";
} else {
int m = net.edges[t].size();
int curr;
for (int i = 0; i < m; ++i) {
if (net.edges[t][i].mark) {
net.edges[t][i].cap = 0;
net.edges[net.edges[t][i].to][net.edges[t][i].rev].cap = 0;
curr = net.edges[t][i].flow; // WARN: real flow
break;
}
}
cout << curr - net.run(t, s) << '\n';
}
}