uva 11380(最大流+拆点）

1 #include<iostream>
2 #include<cstdio>
3 #include<cstring>
4 #include<algorithm>
5 #include<queue>
6 using namespace std;
7 #define MAXN 2222
8 #define inf 1<<30
9
10 struct Edge{
11     int v,cap,next;
12 }edge[MAXN*MAXN];
13
14 int n,m,p,NE,NV,vs,vt;
15 int head[MAXN];
16
17 void Insert(int u,int v,int cap)
18 {
19     edge[NE].v=v;
20     edge[NE].cap=cap;
21     edge[NE].next=head[u];
22     head[u]=NE++;
23
24     edge[NE].v=u;
25     edge[NE].cap=0;
26     edge[NE].next=head[v];
27     head[v]=NE++;
28 }
29
30 int level[MAXN],gap[MAXN];
31 void bfs(int vt)
32 {
33     memset(level,-1,sizeof(level));
34     memset(gap,0,sizeof(gap));
35     level[vt]=0;
36     gap[0]++;
37     queue<int>que;
38     que.push(vt);
39     while(!que.empty()){
40         int u=que.front();
41         que.pop();
42         for(int i=head[u];i!=-1;i=edge[i].next){
43             int v=edge[i].v;
44             if(level[v]!=-1)continue;
45             level[v]=level[u]+1;
46             gap[level[v]]++;
47             que.push(v);
48         }
49     }
50 }
51
52 int cur[MAXN],pre[MAXN];
53 int SAP(int vs,int vt)
54 {
55     bfs(vt);
56     memset(pre,-1,sizeof(pre));
57     memcpy(cur,head,sizeof(head));
58     int u=pre[vs]=vs,aug=inf,maxflow=0;
59     gap[0]=NV;
60     while(level[vs]<NV){
61         bool flag=false;
62         for(int &i=cur[u];i!=-1;i=edge[i].next){
63             int v=edge[i].v;
64             if(edge[i].cap>0&&level[u]==level[v]+1){
65                 flag=true;
66                 aug=min(aug,edge[i].cap);
67                 pre[v]=u;
68                 u=v;
69                 if(v==vt){
70                     maxflow+=aug;
71                     for(u=pre[u];v!=vs;v=u,u=pre[u]){
72                         edge[cur[u]].cap-=aug;
73                         edge[cur[u]^1].cap+=aug;
74                     }
75                     aug=inf;
76                 }
77                 break;
78             }
79         }
80         if(flag)continue;
81         int minlevel=NV;
82         for(int i=head[u];i!=-1;i=edge[i].next){
83             int v=edge[i].v;
84             if(edge[i].cap>0&&level[v]<minlevel){
85                 minlevel=level[v];
86                 cur[u]=i;
87             }
88         }
89         if(--gap[level[u]]==0)break;
90         level[u]=minlevel+1;
91         gap[level[u]]++;
92         u=pre[u];
93     }
94     return maxflow;
95 }
96
97 char map[44][44];
98 int dir[4][2]={{-1,0},{1,0},{0,-1},{0,1}};
99
100 int main()
101 {
102     while(~scanf("%d%d%d",&n,&m,&p)){
103         for(int i=0;i<n;i++)scanf("%s",map[i]);
104         NE=0;
105         vs=0,vt=2*n*m+1,NV=2*n*m+2;
106         memset(head,-1,sizeof(head));
107         for(int i=0;i<n;i++){
108             for(int j=0;j<m;j++){
109                 if(map[i][j]=='~')continue;
110                 for(int k=0;k<4;k++){
111                     int x=i+dir[k][0],y=j+dir[k][1];
112                     if(x<0||x>=n||y<0||y>=m)continue;
113                     Insert(i*m+j+1+n*m,x*m+y+1,inf);
114                 }
115                 if(map[i][j]=='*'){
116                     Insert(vs,i*m+j+1,1);
117                     Insert(i*m+j+1,i*m+j+1+n*m,1);
118                 }
119                 else if(map[i][j]=='.')Insert(i*m+j+1,i*m+j+1+n*m,1);
120                 else if(map[i][j]=='@')Insert(i*m+j+1,i*m+j+1+n*m,inf);
121                 else if(map[i][j]=='#')Insert(i*m+j+1,i*m+j+1+n*m,inf),Insert(i*m+j+1+n*m,vt,p);
122             }
123         }
124         printf("%d\n",SAP(vs,vt));
125     }
126     return 0;
127 }