Add graph/examples/minimum_flow_with_demands.cc

Signed-off-by: subcrip <contact@subc.rip>

graph/examples/minimum_flow_with_demands.cc

@@ -0,0 +1,41 @@
+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';
+    }
+}