WustOJ 1575 Gingers and Mints(快速幂 + dfs )

#include<cstdio>
#include<cstring>
using namespace std;

#define maxn 200
char pic[maxn][maxn];
int vis[maxn][maxn];
int dx[4] = {-1,1,0,0};
int dy[4] = {0,0,-1,1};
int n,m;

void dfs(int x, int y)
{
    for(int i = 0; i < 4; i++)
    {
        int nx = x + dx[i];
        int ny = y + dy[i];
        if(!vis[nx][ny] && pic[nx][ny] == ‘Y‘ && nx >= 0 && nx < n && ny >= 0 && ny < m)
        {
            vis[nx][ny] = 1;
            dfs(nx,ny);
        }
    }
}
int pow_mod(int a,int n,int m)
{

    if(n==0)
    return  1;
    int x=pow_mod(a,n/2,m);
    long long ans=(long long)x*x%m;
    if(n%2==1)
        ans=ans*a%m;
    return (int )ans;
}

int main()
{
    int t;
    scanf("%d", &t);
    while(t--)
    {
        scanf("%d%d", &n, &m);
        memset(vis, 0, sizeof vis);
        for(int i = 0; i < n; i++)
            scanf("%s", pic[i]);
        int cnt = 0;
        for(int i = 0; i < n; i++)
            for(int j = 0; j < m; j++)
            {
                if(!vis[i][j] && pic[i][j] == ‘Y‘)
                {
                    vis[i][j] = 1;
                    cnt++;
                    dfs(i,j);
                }
            }
            printf("%d\n",pow_mod(2,cnt-1,1000000007));
    }
    return 0;
}