HDU 3046 Pleasant sheep and big big wolf

 1 #include <iostream>
 2 #include <cstdio>
 3 #include <cstring>
 4 #include <cmath>
 5 #include <algorithm>
 6 #include <climits>
 7 #include <vector>
 8 #include <queue>
 9 #include <cstdlib>
10 #include <string>
11 #include <set>
12 #include <stack>
13 #define LL long long
14 #define pii pair<int,int>
15 #define INF 0x3f3f3f3f
16 using namespace std;
17 const int maxn = 210*210;
18 struct arc{
19     int to,flow,next;
20     arc(int x = 0,int y = 0,int z = -1){
21         to = x;
22         flow = y;
23         next = z;
24     }
25 };
26 arc e[maxn<<2];
27 int head[maxn],d[maxn],cur[maxn];
28 int tot,S,T,n,m;
29 void add(int u,int v,int flow){
30     e[tot] = arc(v,flow,head[u]);
31     head[u] = tot++;
32     e[tot] = arc(u,flow,head[v]);//可以不这么建图。。。。
33     head[v] = tot++;
34 }
35 bool bfs(){
36     memset(d,-1,sizeof(d));
37     queue<int>q;
38     q.push(T);
39     d[T] = 1;
40     while(!q.empty()){
41         int u = q.front();
42         q.pop();
43         for(int i = head[u]; ~i; i = e[i].next){
44             if(e[i^1].flow && d[e[i].to] == -1){
45                 d[e[i].to] = d[u] + 1;
46                 q.push(e[i].to);
47             }
48         }
49     }
50     return d[S] > -1;
51 }
52 int dfs(int u,int low){
53     if(u == T) return low;
54     int tmp = 0,a;
55     for(int &i = cur[u]; ~i; i = e[i].next){
56         if(e[i].flow && d[e[i].to]+1==d[u]&&(a=dfs(e[i].to,min(low,e[i].flow)))){
57             e[i].flow -= a;
58             e[i^1].flow += a;
59             low -= a;
60             tmp += a;
61             if(!low) break;
62         }
63     }
64     if(!tmp) d[u] = -1;
65     return tmp;
66 }
67 int dinic(){
68     int ans = 0;
69     while(bfs()){
70         memcpy(cur,head,sizeof(head));
71         ans += dfs(S,INF);
72     }
73     return ans;
74 }
75 int main() {
76     int u,v,w,cs = 1;
77     while(~scanf("%d %d",&n,&m)){
78         memset(head,-1,sizeof(head));
79         S = n*m;
80         T = n*m+1;
81         for(int i = tot = 0; i < n; ++i)
82         for(int j = 0; j < m; ++j){
83             scanf("%d",&u);
84             if(i) add(m*(i-1)+j,m*i+j,1);
85             if(j) add(m*i+j-1,m*i+j,1);
86             if(u == 1) add(S,m*i+j,INF);
87             if(u == 2) add(m*i+j,T,INF);
88         }
89         printf("Case %d:\n%d\n",cs++,dinic());
90     }
91     return 0;
92 }