P1141 01迷宫

题见洛谷

#include<iostream>
#include<cstdio>
#include<algorithm>
#include<cstring>
#include<string>
#include<cmath>
#include<vector>
bool f[1005][1005];
char a[1005][1005];
int dx[]={0,0,0,1,-1};int dy[]={0,1,-1,0,0};int n,m;
int num[1009][1009];
using namespace std;
struct H{
    int x;
    int y;
}pos[1000*1000+100];
int bfs(int kx,int ky)
{
    int head=0,tail=1;
    if(!num[kx][ky]){
     pos[head+1].x=kx,pos[head+1].y=ky;f[kx][ky]=true;
     while(head<tail){
      head++;
       for(int i=1;i<=4;i++){
         int nx=pos[head].x+dx[i],ny=pos[head].y+dy[i];
         if(nx<=n&&nx>=1&&ny<=n&&ny>=1)
          if(a[nx][ny]!=a[pos[head].x][pos[head].y]&&!f[nx][ny]){
            pos[++tail].x=nx;pos[tail].y=ny;f[nx][ny]=true;             
          }
       }
     }
     for(int i=1;i<=tail;i++)num[pos[i].x][pos[i].y]=tail;//记忆化 
   }

   return num[kx][ky];
}
int main()
{
    scanf("%d%d",&n,&m);
    for(int i=1;i<=n;i++){
     for(int j=1;j<=n;j++)
        cin>>a[i][j];
    } 
    for(int i=1;i<=m;i++){
        //memset(f,false,sizeof(f));记忆化,不用memset,否则超时 
        int ax,ay;
        scanf("%d%d",&ax,&ay);
        printf("%d
",bfs(ax,ay));
 }
    return 0;   
}