学步园

<span style="font-family: Arial, Helvetica, sans-serif;">#include <cstdio></span>

#include <cstring>
#include <iostream>
using namespace std;
int const MAXN = 110;
char s[MAXN][MAXN];
int dx[] = {0,0,1,-1};
int dy[] = {1,-1,0,0};
int main(){
    int n;
    scanf("%d",&n);
    for(int i = 0;i < n;i++){
        scanf("%s",s[i]);
    }
    bool flag = true;
    for(int i = 0;i < n;i++){
        for(int j = 0;j < n;j++){
           int cnt = 0;
           for(int k = 0;k < 4;k++){
                int x = i + dx[k];
                int y = j + dy[k];
                if(x < 0 || x >= n) continue;
                if(y < 0 || y >= n) continue;
                if(s[x][y] == 'o') cnt++;
           }
           if(cnt & 1){
                flag = false;
                break;
           }
        }
        if(!flag)break;
    }
    if(flag)printf("YES\n");
    else printf("NO\n");
    return 0;
}