DFS 1033 Lake Counting

DFS 1033 Lake Counting

思路

DFS求连通块

在剪枝的时候忘了加 mp[a][b] == '.' ，只能搜第一个连通块，艹

剪枝还是老一套：边界、记忆化搜索、判断对象

遇到水坑W，直接DFS，把连通块全标记，剪枝完成

板子题，不说看代码。

代码

#include <bits/stdc++.h>
using namespace std;
int n, m;
const int N = 105;
char mp[N][N];
int vis[N][N];
int dx[] = {-1, -1, -1, 1, 1, 1, 0, 0};
int dy[] = {0, 1, -1, 0, 1, -1, 1, -1};
 
void dfs(int x, int y)
{
    vis[x][y] = 1;
    for (int i = 0; i < 8; i++) {
        int a = x + dx[i], b = y + dy[i];
        if (a < 1 || b < 1 || a > n || b > m || vis[a][b] || mp[a][b] == '.') continue;
        dfs(a, b);
    }
}
 
int main()
{
    cin >> n >> m;
    int ans = 0;
    for (int i = 1; i <= n; i++)
        for (int j = 1; j <= m; j++)
            cin >> mp[i][j], vis[i][j] = 0;
    for (int i = 1; i <= n; i++) {
        for (int j = 1; j <= m; j++) {
            if (vis[i][j] == 0 && mp[i][j] == 'W') {
                ans ++;
                dfs(i, j);
            }
        }
    }
    cout << ans;
    return 0;
}