广度优先遍历BFS

//    (keng)题目是先输入的方式：列数 * 行数    
/*
    bfs
*/
#include <iostream>
#include <queue>
using namespace std;
const int N = 20;
char graph[N][N];
struct node{
    int x, y;
};
node st;
int main(){
    int n, m;
    while(cin >> m >> n && m && n){
        for(int i = 0; i < n ; i ++){
            for(int j = 0; j < m; j ++){
                cin >> graph[i][j];
                if(graph[i][j] == '@')  st = {i, j};
            }
        }
        queue<node> qu;
        qu.push(st);
        graph[st.x][st.y] = '#';
        int dx[4] = {0, -1, 0, 1}, dy[4] = {-1, 0, 1, 0};
        int cnt = 1;
        while(!qu.empty()){
            node now = qu.front();
            qu.pop();
            for(int i = 0; i < 4; i ++ ){
                int xx = now.x + dx[i];
                int yy = now.y + dy[i];
                if(xx < 0 || xx >= n || yy < 0 || yy >= m)  continue;
                if(graph[xx][yy] == '#')    continue;
                cnt ++ ;
                qu.push({xx, yy});
                graph[xx][yy] = '#';
            }
        }
        cout << cnt << endl;
    }
    return 0;
}

深度优先遍历DFS

/*
    dfs
*/
#include <iostream>
#include <cstring>
using namespace std;
const int N = 30;
char graph[N][N];
bool vis[N][N];
typedef pair<int, int> pii;
pii st;
int n, m;
int cnt;
int dic[4][2] = {
    {-1, 0}, {0, 1}, {1, 0}, {0, -1}  
};
void read(){
    for(int i = 0; i < n; i ++ ){
        for(int j = 0; j < m; j ++ ){
            cin >> graph[i][j];
            if(graph[i][j] == '@')  st = {i, j};
        }
    }
}
bool check(int x, int y){
    return x >= 0 && x < n && y >= 0 && y < m; 
}
void dfs(pii loc){
    for(int i = 0; i < 4; i ++ ){
        int x = loc.first + dic[i][0];
        int y = loc.second + dic[i][1];
        if(check(x, y) && graph[x][y] == '.' && !vis[x][y]){
            vis[x][y] = true;
            cnt ++ ;
            dfs({x, y});
        }
    }
}
int main(){
    while(cin >> m >> n && m && n){
        read();
        memset(vis, false, sizeof vis);
        cnt = 1;
        dfs(st);
        cout << cnt << endl;
    }
    return 0;
}