Island Transport HDU 4280 Dinic模板

Island Transport HDU 4280 Dinic模板

题目链接：https://cn.vjudge.net/contest/163017#problem/G
题目大意：给出N个点的坐标和M条有容量的边，找出从最西边的点到最东边的点的最大流量。
题目分析：抄的李东庆的模板，于是以后就打算用这个板子搞 Dinic 了。

#include <bits/stdc++.h>
using namespace std;

const int maxn = 100000 + 10;
const int INF = 0x3f3f3f3f;

struct node {
   int to, w, next;
}Edge[maxn << 1];

int Head[maxn], cur[maxn], level[maxn], cnt;

void add(int u, int v, int w) {
   Edge[cnt].to = v;
   Edge[cnt].w = w;
   Edge[cnt].next = Head[u];
   Head[u] = cnt++;
   Edge[cnt].to = u;
   Edge[cnt].w = w; //反向边 题目是双向的 单向的话就是0
   Edge[cnt].next = Head[v];
   Head[v] = cnt++;
}

bool bfs(int s, int t) {
   memset(level, -1, sizeof(level));
   queue<int> q;
    level[s] = 0;
    q.push(s);
    while(!q.empty()) {
        int now = q.front();
        q.pop();
        for(int i = Head[now]; ~i; i = Edge[i].next) {
            int to = Edge[i].to;
            if(level[to] == -1 && Edge[i].w) {
                level[to] = level[now] + 1;
                q.push(to);
            }
        }
    }
    return level[t] != -1;
}

int dfs(int s, int t, int f) {
   if(s == t) return f;
   int flow = 0, d;
   for(int &i = cur[s]; ~i; i = Edge[i].next) {
       int to = Edge[i].to;
       if(Edge[i].w && level[s] < level[to] && (d = dfs(to, t, min(f, Edge[i].w)))) {
          f -= d;
          Edge[i].w -= d;
          Edge[i ^ 1].w += d;
          flow += d;
          if(!f) break;
       }
   }
   if(!flow) level[s] = -1;
   return flow;
}

int max_flow(int s, int e) {
   int flow = 0;
   while(bfs(s, e)) {
      memcpy(cur, Head, sizeof(Head));
      flow += dfs(s, e, INF);
   }
   return flow;
}

int main()
{
   int t;
   scanf("%d", &t);
   while(t--) {
      int n, m, s, e, sx = INF, ex = -INF;
      scanf("%d %d", &n, &m);
      for(int i = 1; i <= n; i++) {
         int x, y;
         scanf("%d %d", &x, &y);
         if(sx > x) {sx = x; s = i; }
         if(ex < x) {ex = x; e = i; }
   }

       cnt = 0;
       memset(Head, -1, sizeof(Head));
       for(int i = 0; i < m; i++) {
          int u, v, w;
          scanf("%d %d %d", &u, &v, &w);
          add(u, v, w);
       }

       int v = max_flow(s, e);
       printf("%d\n", v);
   }

}