BZOJ4554: [Tjoi2016&Heoi2016]游戏

#include<cstdio>
#include<cctype>
#include<queue>
#include<cstring>
#include<algorithm>
#define rep(i,s,t) for(int i=s;i<=t;i++)
#define dwn(i,s,t) for(int i=s;i>=t;i--)
#define ren for(int i=first[x];i!=-1;i=next[i])
using namespace std;
const int maxn=3010;
const int maxm=50010;
const int inf=1e9;
struct ISAP{
    struct tedge{int x,y,w,next;}adj[maxm];int ms,fch[maxn];
    int d[maxn],s[maxn],cur[maxn],gap[maxn],n,top;
    void init(){
        ms=0;top=0;
        memset(d,-1,sizeof(d));
        memset(fch,-1,sizeof(fch));
    }
    void AddEdge(int u,int v,int w){
        adj[ms]=(tedge){u,v,w,fch[u]};fch[u]=ms++;
        adj[ms]=(tedge){v,u,0,fch[v]};fch[v]=ms++;
    }
    void bfs(){
        queue<int>Q;Q.push(n);d[n]=0;
        while(!Q.empty()){
            int u=Q.front();Q.pop();
            for(int i=fch[u];i!=-1;i=adj[i].next){
                int v=adj[i].y;
                if(d[v]==-1) d[v]=d[u]+1,Q.push(v);
            }
        } 
    }
    int solve(int S,int T){
        n=T;bfs();int k=S,i,flow=0;
        for(i=0;i<=n;i++) cur[i]=fch[i],gap[d[i]]++;
        while(d[S]<n){
            if(k==n){
                int mi=inf,pos;
                for(i=0;i<top;i++) if(adj[s[i]].w<mi) mi=adj[s[i]].w,pos=i;
                for(i=0;i<top;i++) adj[s[i]].w-=mi,adj[s[i]^1].w+=mi;
                flow+=mi;top=pos;k=adj[s[top]].x;
            }
            for(i=cur[k];i!=-1;i=adj[i].next){
                int v=adj[i].y;
                if(adj[i].w&&d[k]==d[v]+1){cur[k]=i;k=v;s[top++]=i;break;}
            }
            if(i==-1){
                int lim=n;
                for(i=fch[k];i!=-1;i=adj[i].next){
                    int v=adj[i].y;
                    if(adj[i].w&&d[v]<lim) lim=d[v],cur[k]=i;
                } if(--gap[d[k]]==0) break;
                d[k]=lim+1;gap[d[k]]++;
                if(k!=S) k=adj[s[--top]].x;
            }
        } return flow;
    }
}sol;
char Map[55][55];
int n,m,S,T,A[55][55],B[55][55];
int main() {
	scanf("%d%d",&n,&m);
	rep(i,1,n) scanf("%s",Map[i]+1);sol.init();
	rep(i,1,n) {
		S++;
		rep(j,1,m) {
			if(Map[i][j]==‘#‘) S++;
			A[i][j]=S;
		}
	}
	rep(j,1,m) {
		S++;
		rep(i,1,n) {
			if(Map[i][j]==‘#‘) S++;
			B[i][j]=S;
		}
	}
	S++;T=S+1;sol.n=T;
	rep(i,1,A[n][m]) sol.AddEdge(S,i,1);
	rep(i,A[n][m]+1,B[n][m]) sol.AddEdge(i,T,1);
	rep(i,1,n) rep(j,1,m) if(Map[i][j]==‘*‘) sol.AddEdge(A[i][j],B[i][j],1);
	printf("%d\n",sol.solve(S,T));
	return 0;
}