POJ 1979

POJ 1979

BFS 连通块

输入的(n) 和(m) 是反的要注意

#include <iostream>
#include <cstdio>
#include <cstring>
#include <algorithm>
#include <queue>
using namespace std;
#define endl '
'
const int N = 200;
char g[N][N];
int n,m,ans,sx,sy;
int dx[4] = {0,0,1,-1};
int dy[4] = {1,-1,0,0};
bool st[N][N];
struct node {
    int x,y;
};
void bfs(int x,int y) {
    queue<node> q;
    q.push({x,y});
    st[x][y] = 1;
    while(q.size()) {
        node t = q.front();
        q.pop();
        for(int i = 0;i < 8; ++i) {
            int nx = t.x + dx[i],ny = t.y + dy[i];
            if(nx >= 0 && nx < n && ny >= 0 && ny < m && g[nx][ny] == '.' && !st[nx][ny]) {
                q.push({nx,ny});
                st[nx][ny] = 1;
                ans ++;
            }
        }
    }
}
int main() {
    ios::sync_with_stdio(0),cin.tie(0),cout.tie(0);
    while(cin >> m >> n && n && m) {
        memset(st,0,sizeof st);
        ans = 1;
        for(int i = 0;i < n; ++i)
            for(int j = 0;j < m; ++j) {
                cin >> g[i][j];
                if(g[i][j] == '@') sx = i,sy = j;
            }
        bfs(sx,sy);
        cout << ans << endl;
    }
    return 0;
}