Game (思维)

#include<bits/stdc++.h>
using namespace std;

const int maxn = 1007;
char str[maxn][maxn];
int cntx[maxn], cnty[maxn],x[maxn],y[maxn];

int main(void){
    int T,n,m;scanf("%d",&T)；
    while(T --){
        scanf("%d%d",&n,&m);
        int tot = 0;
        memset(cntx, 0, sizeof(cntx));
        memset(cnty, 0, sizeof(cnty));
        memset(x, -1, sizeof(x));
        memset(y, -1, sizeof(y));
        for(int i = 0; i < n; i ++){
            scanf("%s", str[i]);
            for(int j = 0; j < m; j ++){
                if(str[i][j] == '#'){
                    cntx[i] ++;cnty[j] ++;
                    tot ++;
                }else{
                    x[i] = j;y[j] = i;
                }
            }
        }
        long long ans = 0;
        for(int i = 0; i < n; i ++)
            for(int j = i + 1; j < n; j ++)
                ans += (long long)(j - i) * cntx[i] * cntx[j] * 2;
        for(int i = 0; i < m; i ++)
            for(int j = i + 1; j < m; j ++)
                ans += (long long)(j - i) * cnty[i] * cnty[j] * 2;

        int cnt = 0;
        for(int i = 0; i < n; i ++){
            if(x[i] == -1) cnt = 0;
            else if(i == 0 || x[i] <= x[i - 1]) cnt = x[i];
            else cnt += x[i];
            if(x[i] != -1)
                ans += 4LL * cnt * (m - x[i] - 1);
        }
        cnt = 0;
        for(int i = 0; i < n; i ++){
            if((i == 0)||(x[i] > x[i - 1])||(x[i] == -1)) cnt = m - x[i] - 1;
            else cnt += m - x[i] - 1;
            if(x[i] >= 0)
                ans += 4LL * (cnt - m + x[i] + 1) * (x[i]>0?x[i]:0);
        }

        cnt = 0;
        for(int i = 0; i < m; i ++){
            if(y[i] == -1) cnt = 0;
            else if(i == 0 || y[i] <= y[i - 1]) cnt = y[i];
            else cnt += y[i];

            ans += 4LL * cnt * (n - y[i] - 1);
        }
        cnt = 0;
        for(int i = 0; i < m; i ++){
            if((i == 0)||(y[i] > y[i - 1])||(y[i] == -1)) cnt = n - y[i] - 1;
            else cnt += n - y[i] - 1;
            if(y[i] >= 0)
                ans += 4LL * (cnt - n + y[i] + 1) * (y[i]>0?y[i]:0);
        }

        printf("%.4lf
",(double)ans/tot/tot);
    }
    return 0;
}