自己写的BFS代码

#include<bits/stdc++.h>
using namespace std;
int r, c;
char a[21][21];
int startx, starty;
bool vis[21][21];
int dx[4] = { 1,-1,0,0 };
int dy[4] = { 0,0,1,-1 };
int ans = 1;
void bfs(int x, int y) {
    queue<pair<int, int> > q;
    q.push(make_pair(x,y));
    vis[x][y] = true;
    while (!q.empty()) {
        pair<int, int> now;
        now = q.front();
        q.pop();
        for (int i = 0; i < 4; i++) {
            for (int j = 0; j < 4; j++) {
                int xx = now.first + dx[i];
                int yy = now.second + dy[i];
                if (xx >= 0 && xx < c && yy >= 0 && yy < r && !vis[xx][yy] && a[xx][yy] == '.') {
                    q.push(make_pair(xx, yy));
                    vis[xx][yy] = true;
                    ans++;

                }
            }
        }

    }


}
int num1, num2;
int main()
{
    cin >> r >> c;
    while(1){
    memset(vis, false, sizeof(vis));
    memset(a,0,sizeof(a));
    ans=1;
    for (int i = 0; i < c; i++) {
        cin >> a[i];
    }
    for (int i = 0; i < c; i++) {
        for (int j = 0; j < r; j++) {
            if (a[i][j] == '@') {
                startx = i;
                starty = j;
                break;
            }
        }
    }
    bfs(startx, starty);
    cout << ans << endl;
    cin >> r >> c;
    if(r==0&&c==0)
        break;

    }
    return 0;
}

y总 dfs的实现

#include<bits/stdc++.h>
using namespace std;

const int N = 25;
int n, m;
char g[N][N];
bool st[N][N];

int dx[4] = { -1,0,1,0 };
int dy[4] = { 0,1,0,-1 };
int dfs(int x, int y) {
    int cnt = 1;
    st[x][y] = true;
    for (int i = 0; i < 4; i++) {
        int a = x + dx[i];
        int b = y + dy[i];
        if (a < 0 || a >= n || b < 0 || b >= m)continue;
        if (g[a][b] != '.')continue;
        if (st[a][b])continue;
        cnt += dfs(a, b);
    }
    return cnt;
}
int main()
{
    while (cin >> m >> n, n || m) {
        for (int i = 0; i < n; i++)
            cin >> g[i];
        int x, y;
        for (int i = 0; i < n; i++) {
            for (int j = 0; j < m; j++) {
                if (g[i][j] == '@') {
                    x = i;
                    y = j;
                }
            }
        }
        memset(st, 0, sizeof(st));
        cout << dfs(x, y) << endl;
    }

    return 0;
}