【图论】[ZOJ1054]Place the Robots

题目

分析:二分图匹配,和ZOJ1052差不多,但是草地在计算连通块是当做空地,在连边是如果交点是草地则不连边。

代码:

#include<cstdio>
#include<cstring>
#define MAXN 50
int n,a[MAXN+10][MAXN+10],cnt,cnt1,c[MAXN*MAXN*2+10],ans,T,m;
char s[MAXN+10][MAXN+10];
bool vis[MAXN*MAXN*2+10];
struct node{
    int v;
    node *next;
}edge[MAXN*MAXN*MAXN*MAXN/4+10],*adj[MAXN*MAXN*2+10],*ecnt=edge;
void addedge(int u,int v){
    node *p=++ecnt;
    p->v=v;
    p->next=adj[u];
    adj[u]=p;
}
bool dfs(int u){
    int v;
    for(node *p=adj[u];p;p=p->next){
        v=p->v;
        if(!vis[v]){
            vis[v]=1;
            if(!c[v]||dfs(c[v])){
                c[u]=v;
                c[v]=u;
                return 1;
            }
        }
    }
    return 0;
}
void maxmatch(){
    for(int i=1;i<=cnt1;i++){
        memset(vis,0,sizeof vis);
        if(!c[i]&&dfs(i))
            ans++;
    }
}
int main()
{
    int i,j,tcnt=0;
    scanf("%d",&T);
    while(T--){
        scanf("%d%d",&n,&m);
        memset(c,0,sizeof c);
        memset(adj,0,sizeof adj);
        memset(a,0,sizeof a);
        ans=cnt=0;
        ecnt=edge;
        for(i=1;i<=n;i++)
            scanf("%s",s[i]+1);
        for(i=1;i<=n;i++)
            for(j=1;j<=m;j++){
                if(s[i][j]=='#')
                    continue;
                if(!s[i][j-1]||s[i][j-1]=='#')
                    cnt++;
                if(s[i][j]=='*')
                    continue;
                a[i][j]=cnt;
            }
        cnt1=cnt;
        for(j=1;j<=m;j++)
            for(i=1;i<=n;i++){
                if(s[i][j]=='#')
                    continue;
                if(!s[i-1][j]||s[i-1][j]=='#')
                    cnt++;
                if(s[i][j]=='*')
                    continue;
                addedge(a[i][j],cnt);
                addedge(cnt,a[i][j]);
        }
        maxmatch();
        printf("Case :%d\n%d\n",++tcnt,ans);
    }
}

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