BZOJ 4997 [Usaco2017 Feb]Why Did the Cow Cross the Road III

本来想做一道搜索

最后发现是一道并查集的水题

如果两个邻格之间没有路

就把他们合并就行了

#include <cstdio>
#include <cstring>
#include <iostream>
#include <algorithm>
using namespace std;
const int MAXN=105;
const int MAXM=20005;
inline int read(){int x=0,f=1,ch=getchar();while(ch<'0'||ch>'9'){if(ch=='-')f=-1;ch=getchar();}while(ch>='0'&&ch<='9'){x=x*10+ch-'0';ch=getchar();}return x*f;
}
int f[MAXM];
inline int find(int x){return f[x]=(f[x]==x)?f[x]:find(f[x]);
}
inline bool same(int x,int y){return find(x)==find(y);
}
inline void add(int x,int y){f[find(x)]=find(y);
}
int a[MAXN][MAXN];
int b[MAXN][MAXN];
int siz[MAXM];
int q[MAXM],tail;
int main(){int n=read(),k=read(),r=read();for(int i=1;i<=n;i++)for(int j=1;j<=n;j++)f[i*n+j]=i*n+j;for(int i=1;i<=r;i++){int r1=read(),c1=read(),r2=read(),c2=read();if(r1==r2+1) a[r2][c1]=1;if(r2==r1+1) a[r1][c1]=1;if(c1==c2+1) b[r1][c2]=1;if(c2==c1+1) b[r1][c1]=1;}for(int i=1;i<=n;i++)for(int j=1;j<=n;j++){if(!a[i][j]&&i<n) add(i*n+j,i*n+j+n);if(!b[i][j]&&j<n) add(i*n+j,i*n+j+1);}for(int i=1;i<=k;i++){int r=read(),c=read();if(!siz[find(r*n+c)]) q[++tail]=find(r*n+c);siz[find(r*n+c)]++;}int ans=0;// cout<<tail<<endl;for(int i=1;i<=tail;i++) ans+=siz[q[i]]*(k-siz[q[i]]),k-=siz[q[i]];printf("%d\n",ans);return 0;
}