P3376 【模板】网络最大流

https://www.luogu.com.cn/record/91932491

Luogu/P3376/P3376.cpp

@@ -1,5 +1,5 @@
 #include <iostream>
-#include <cstring>
+#include <algorithm>
 #include <queue>
 
 using std::cin;
@@ -8,44 +8,45 @@ const char endl = '\n';
 
 const int N = 205,
           M = 5005;
+const int INF = 0x3f3f3f3f;
 
 int n, m, s, t, flow;
 long long ans;
-
+int idx, head[N], ver[M << 1], edge[M << 1], next[M << 1];
-// Graph
+int d[N], cur[N];
-int idx, head[N], edge[M << 1], ver[M << 1], next[M << 1];
 
 void add(int u, int v, int w) {
     next[idx] = head[u];
-    edge[idx] = w;
     ver[idx] = v;
+    edge[idx] = w;
     head[u] = idx++;
 }
 
-// Dinic
-int d[N], cur[N];
-
 bool bfs() {
-    memset(d, 0x00, sizeof(d));
+    std::fill_n(d, N, 0);
+
     std::queue<int> q;
-    d[s] = 1;
     q.push(s);
+    d[s] = 1;
     cur[s] = head[s];
 
     while (!q.empty()) {
         int u = q.front();
         q.pop();
+
         for (int i = head[u]; ~i; i = next[i]) {
             int v = ver[i],
                 w = edge[i];
+
             if (w && !d[v]) {
                 d[v] = d[u] + 1;
                 cur[v] = head[v];
                 if (v == t) return true;
-                q.push(v);
+                q.emplace(v);
             }
         }
     }
+
     return false;
 }
 
@@ -58,30 +59,41 @@ int dinic(int u, int limit) {
 
         int v = ver[i],
             w = edge[i];
+
         if (w && d[v] == d[u] + 1) {
-            int k = dinic(v, std::min(edge[i], limit - flow));
+            int k = dinic(v, std::min(w, limit - flow));
+
             if (!k) d[v] = 0;
+
             edge[i] -= k;
             edge[i ^ 1] += k;
             flow += k;
         }
     }
+
     return flow;
 }
 
 int main() {
     std::ios::sync_with_stdio(false);
-    memset(head, 0xff, sizeof(head));
+    cin.tie(nullptr);
+
+    std::fill_n(head, N, -1);
+
     cin >> n >> m >> s >> t;
-    for (int i = 1; i <= m; i++) {
+
-        int u, v, w;
+    for (int i = 1, u, v, w; i <= m; i++) {
         cin >> u >> v >> w;
+
         add(u, v, w);
         add(v, u, 0);
     }
+
     while (bfs()) {
-        while (flow = dinic(s, 0x3f3f3f3f)) ans += flow;
+        while (flow = dinic(s, INF)) ans += flow;
     }
+
     cout << ans << endl;
+
     return 0;
 }