算法1
(BFS) $O(n * m * k)$
时间复杂度
n * m * k(组数)
C++ 代码
// 个人感觉bfs会好一点
#include <iostream>
#include <stdio.h>
#include <algorithm>
#include <queue>
using namespace std;
const int N = 30;
int m, n;
queue<pair<int, int>> q;
char f[N][N];
int dx[] = {0, -1, 0, 1}, dy[] = {-1, 0, 1, 0};
void find(int m, int n)
{
int res = 0;
for(int i = 0; i < m; i ++)
for(int j = 0; j < n; j ++)
{
cin >> f[i][j];
if(f[i][j] == '@') q.push({i, j});
}
while(q.size())
{
res ++;
auto t = q.front();
q.pop();
for(int i = 0; i < 4; i ++)
{
int x = t.first + dx[i], y = t.second + dy[i];
if(x >= 0 && x < m && y >= 0 && y < n && f[x][y] == '.')
{
q.push({x, y}), f[x][y] = '@';
}
}
}
cout << res << endl;
}
int main()
{
int m, n;
while(true)
{
cin >> n >> m;
if(n == 0 && m == 0) return 0;
else find(m, n);
}
}