bzoj 1001 [BeiJing2006]狼抓兔子

 1 /**************************************************************
 2     Problem: 1001
 3     User: Doggu
 4     Language: C++
 5     Result: Accepted
 6     Time:2032 ms
 7     Memory:122924 kb
 8 ****************************************************************/
 9  
10 #include <cstdio>
11 #include <algorithm>
12 #include <cstring>
13 #include <queue>
14 #define pos(x,y) ((x-1)*m+y)
15  
16 const int M = 7000000 + 10;
17 const int N = 1000000 + 10;
18 struct Edge {int v, upre, cap, flow;}g[M];
19 int head[N], ne = 0;
20 inline void adde(int u,int v,int cap) {
21     //printf("ADDE:%d %d %d\n",u,v,cap);
22     g[ne]=(Edge){v,head[u],cap,0};head[u]=ne++;
23     g[ne]=(Edge){u,head[v],cap,0};head[v]=ne++;
24 }
25  
26 int n, m, u, v, cap, s, t;
27 struct DINIC {
28     int d[N];
29     bool vis[N];
30     std::queue<int> q;
31     bool BFS() {//建立层次图 
32         memset(vis, 0, sizeof(vis));
33         while(!q.empty()) q.pop();
34         vis[s] = 1;d[s] = 0;q.push(s);
35         while(!q.empty()) {
36             int u = q.front();q.pop();
37             for( int i = head[u]; i != -1; i = g[i].upre ) {
38                 int v = g[i].v;
39                 if(!vis[v] && g[i].cap>g[i].flow) vis[v] = 1, d[v] = d[u] + 1, q.push(v);
40             }
41         }
42         return vis[t];
43     }   
44      
45     int cur[N];
46     int DFS(int u,int a) {//找增广路 
47         if(u == t||a == 0) return a;//注意是return a 
48         int f, flow = 0;
49         for( int& i = cur[u]; i != -1; i = g[i].upre ) {//不要忘了加cur 
50             int v = g[i].v;
51             if(d[u] + 1 == d[v] && (f=DFS(v,std::min(a,g[i].cap-g[i].flow)))>0) {
52                 g[i].flow+=f;g[i^1].flow-=f;flow+=f;a-=f;//加加减减 
53                 if(a==0) break;
54             }
55         }
56         return flow;
57     }
58     void maxflow() {
59         int flow = 0;
60         while(BFS()) {
61             memcpy(cur,head,sizeof(head));//每一次清零 
62             flow += DFS(s,0x3f3f3f3f);
63         }
64         printf("%d\n",flow);
65     }
66 }dinic;
67 int main() {
68     memset(head,-1,sizeof(head));
69     scanf("%d%d",&n,&m);
70     for( int x = 1; x <= n; x++ ) for( int y = 1; y < m; y++ ) {
71         scanf("%d",&cap);
72         adde(pos(x,y),pos(x,y+1),cap);
73         //adde(pos(x,y+1),pos(x,y),cap);
74     }
75     for( int x = 1; x < n; x++ ) for( int y = 1; y <= m; y++ ) {
76         scanf("%d",&cap);
77         adde(pos(x,y),pos(x+1,y),cap);
78         //adde(pos(x+1,y),pos(x,y),cap);
79     }
80     for( int x = 1; x < n; x++ ) for( int y = 1; y < m; y++ ) {
81         scanf("%d",&cap);
82         adde(pos(x,y),pos(x+1,y+1),cap);
83         //adde(pos(x+1,y+1),pos(x,y),cap);
84     }
85     s=pos(1,1);t=pos(n,m);
86     dinic.maxflow();
87     return 0;
88 }
89