poj 3469

 1 #include <iostream>
 2 #include <cstdio>
 3 #include <cstring>
 4 #include <algorithm>
 5 #include <vector>
 6 #include <queue>
 7 
 8 using namespace std;
 9 
10 const int MAX_N = 20005;
11 const int INF = (1 << 30);
12 int N,M;
13 struct Edge{ int from, to, cap, flow; };
14 vector<Edge> edges;
15 int cur[MAX_N],d[MAX_N];
16 vector<int> G[MAX_N];
17 bool vis[MAX_N];
18 
19 void add_edge(int from, int to, int cap) {
20         edges.push_back(Edge {from, to, cap, 0});
21         edges.push_back(Edge {to, from, 0, 0});
22         int m = edges.size();
23         G[from].push_back(m - 2);
24         G[to].push_back(m - 1);
25 }
26 
27 bool bfs(int s,int t) {
28 
29         memset(vis,0,sizeof(vis));
30         queue<int> q;
31         q.push(s);
32         d[s] = 0;
33         vis[s] = 1;
34         while (!q.empty()) {
35                 int x = q.front(); q.pop();
36                 for (int i = 0; i < G[x].size(); ++i) {
37                        Edge& e = edges[ G[x][i] ];
38                        if (!vis[e.to] && e.cap > e.flow) {
39                                 d[e.to] = d[x] + 1;
40                                 vis[e.to] = 1;
41                                 q.push(e.to);
42                        }
43                 }
44         }
45 
46         return vis[t];
47 }
48 
49 int dfs(int x, int a, int t) {
50         if(x == t || a == 0) return a;
51         int flow = 0,f;
52         for(int& i = cur[x]; i < G[x].size(); ++i) {
53                 Edge& e = edges[ G[x][i] ];
54                 if(d[x] + 1 == d[e.to] && (f = dfs(e.to,min(a,e.cap - e.flow),t)) > 0) {
55                         e.flow += f;
56                         edges[ G[x][i] ^ 1].flow -= f;
57                         a -= f;
58                         flow += f;
59                         if(a == 0) break;
60 
61                 }
62 
63         }
64 
65         return flow;
66 }
67 
68 int Maxflow(int s, int t) {
69 
70         int flow = 0;
71         while (bfs(s,t)) {
72                 //printf("fuck\n");
73                 memset(cur,0,sizeof(cur));
74                 flow += dfs(s, INF, t);
75         }
76         return flow;
77 }
78 int main()
79 {
80     //freopen("sw.in","r",stdin);
81     scanf("%d%d", &N, &M);
82     for (int i = 1; i <= N; ++i) {
83             int a,b;
84             scanf("%d%d", &a, &b);
85             add_edge(0,i,a);
86             add_edge(i,N + 1,b);
87     }
88 
89     for (int i = 1; i <= M; ++i) {
90             int a,b,w;
91             scanf("%d%d%d",&a,&b,&w);
92             add_edge(a,b,w);
93             add_edge(b,a,w);
94     }
95 
96     printf("%d\n",Maxflow(0,N + 1));
97     //cout << "Hello world!" << endl;
98     return 0;
99 }