Queen on Grid_dp

思想很单纯-> dp

Code:
代码解释：

dp[i][j] += ans[1][i-1][j];///竖着过来
dp[i][j] %= mod;
dp[i][j] += ans[2][i][j-1];///横着过来
dp[i][j] %= mod;
dp[i][j] += ans[3][i-1][j-1];///斜着过来

dp加上之后，注意进行取模
然后再更新这一个节点的计数（ans）

ans[1][i][j] = (ans[1][i-1][j] + dp[i][j]) % mod;
ans[2][i][j] = (ans[2][i][j-1] + dp[i][j]) % mod;
ans[3][i][j] = (ans[3][i-1][j-1] + dp[i][j]) % mod;

char s[2008][2008];
ll ans[4][2008][2008];
ll dp[2008][2008];
int main()
{
    int n = read,m = read;
    dp[1][1] = 1;
    for(int i = 1;i <= n;i++) cin >> s[i] + 1;
    for(int i=1;i<=n;i++){
        for(int j=1;j<=m;j++){
            if(s[i][j] == '#'){
                ans[1][i][j] = 0;
                ans[2][i][j] = 0;
                ans[3][i][j] = 0;
                continue;
            }
            dp[i][j] += ans[1][i-1][j];
            dp[i][j] %= mod;
            dp[i][j] += ans[2][i][j-1];
            dp[i][j] %= mod;
            dp[i][j] += ans[3][i-1][j-1];
            dp[i][j] %= mod;
            ans[1][i][j] = (ans[1][i-1][j] + dp[i][j]) % mod;
            ans[2][i][j] = (ans[2][i][j-1] + dp[i][j]) % mod;
            ans[3][i][j] = (ans[3][i-1][j-1] + dp[i][j]) % mod;
        }
    }
    cout << dp[n][m] <<endl;
    return 0;
}