洛谷P1141【01迷宫】

#include<bits/stdc++.h>
using namespace std;
#define check(x,y) (x>0&&x<=n&&y>0&&y<=n)
#define nx (x+dx[i])
#define ny (y+dy[i]) 
char a[1005][1005]; 
int f[1005][1005]; bool v[1005][1005];
int n, m,now;
const int dx[4] = { 1, 0, -1, 0 }, dy[4] = { 0, 1, 0, -1 };
int ans[1000005];
void dfs(int x, int y, int idx){
    now++;
    f[x][y] = idx;
    for (int i = 0; i<4; i++){
        if (check(nx, ny) && !v[nx][ny] && a[x][y] != a[nx][ny]){
            v[nx][ny] = true;
            dfs(nx, ny,idx);
        }
    }
}
int res;
int main(){
    scanf("%d%d", &n, &m);
    int idx = 0;
    for (int i = 1; i <= n; i++) scanf("%s", a[i] + 1);
    for (int i = 1; i <= n; i++)
    for (int j = 1; j <= n; j++) if (!v[i][j]){
        v[i][j] = true; 
　　　　 now = 0;
        dfs(i,j,idx);
        ans[idx] = now;
        idx++;
    }
    int x, y;
    for (int i = 1; i <= m; i++){
        scanf("%d%d", &x, &y);
        printf("%d\n", ans[f[x][y]]);
    }
    return 0;
}