#340. 收藏家

https://sjzezoj.com/submission/66655

S2OJ/340/340.cpp

@@ -0,0 +1,121 @@
+#include <iostream>
+#include <functional>
+#include <queue>
+#include <tuple>
+#include <vector>
+
+using std::cin;
+using std::cout;
+const char endl = '\n';
+
+const int INF = 0x3f3f3f3f;
+
+int main() {
+    std::ios::sync_with_stdio(false);
+    cin.tie(nullptr);
+
+    int t;
+
+    cin >> t;
+
+    while (t--) {
+        int n, m;
+
+        cin >> n >> m;
+
+        int s = 0, t = 1;
+        std::vector<int> a(n + 1), pre(n + 1), head((m + 1) << 1, -1);
+        std::vector<std::tuple<int, int, int>> edges;
+
+        for (int i = 1; i <= n; i++) {
+            cin >> a[i];
+        }
+
+        std::function<void(int, int, int)> add = [&](int u, int v, int w) -> void {
+            edges.emplace_back(v, w, head[u]);
+            head[u] = edges.size() - 1;
+        };
+
+        for (int i = 1, x, y; i <= m; i++) {
+            cin >> x >> y;
+
+            add(i << 1, i << 1 | 1, 1);
+            add(i << 1 | 1, i << 1, 1);
+
+            add(pre[x], i << 1, pre[x] ? a[x] : 1);
+            add(i << 1, pre[x], 0);
+            pre[x] = i << 1;
+
+            add(pre[y], i << 1 | 1, pre[y] ? a[y] : 1);
+            add(i << 1 | 1, pre[y], 0);
+            pre[y] = i << 1 | 1;
+        }
+
+        add(pre[1], t, a[1]);
+        add(t, pre[1], 0);
+
+        std::vector<int> dist((m + 1) << 1);
+
+        std::function<bool()> bfs = [&]() -> bool {
+            std::fill(dist.begin(), dist.end(), 0);
+
+            std::queue<int> q;
+
+            q.emplace(s);
+            dist[s] = 1;
+
+            while (!q.empty()) {
+                int u = q.front();
+                q.pop();
+
+                for (int i = head[u]; ~i; i = std::get<2>(edges[i])) {
+                    int v = std::get<0>(edges[i]),
+                        w = std::get<1>(edges[i]);
+
+                    if (!dist[v] && w) {
+                        dist[v] = dist[u] + 1;
+
+                        if (v == t) return true;
+
+                        q.emplace(v);
+                    }
+                }
+            }
+
+            return false;
+        };
+
+        std::function<int(int, int)> dinic = [&](int u, int limit) -> int {
+            if (u == t) return limit;
+
+            int flow = 0;
+
+            for (int i = head[u]; ~i; i = std::get<2>(edges[i])) {
+                int v = std::get<0>(edges[i]),
+                    w = std::get<1>(edges[i]);
+
+                if (dist[v] == dist[u] + 1 && w) {
+                    int k = dinic(v, std::min(w, limit - flow));
+
+                    if (!k) dist[v] = 0;
+
+                    std::get<1>(edges[i]) -= k;
+                    std::get<1>(edges[i ^ 1]) += k;
+                    flow += k;
+                }
+            }
+
+            return flow;
+        };
+
+        int res = 0;
+
+        while (bfs()) {
+            while (int flow = dinic(s, INF)) res += flow;
+        }
+
+        cout << res << endl;
+    }
+
+    return 0;
+}