//简单搜索，只要走遍所有可达的路径

BFS版:

#include "iostream"#include "cstdio"#include "memory.h"#include "queue"using namespace std;const int MAX = 22;const int dx[] = {1,-1,0,0},dy[] = {0,0,1,-1};char map[MAX][MAX];int vis[MAX][MAX];int x,y;int n,m;pair<int ,int> now;int bfs(){    int cnt = 1;    memset(vis,0,sizeof(vis));    queue< pair<int,int> > que;    que.push(make_pair(x,y));    vis[x][y] = 1;    while (!que.empty()) {        now = que.front();        que.pop();        int i,tx,ty;        for (i = 0;i < 4; ++ i) {            tx = now.first + dx[i];            ty = now.second + dy[i];            if (tx < 0 || ty < 0|| tx >= m || ty >= n) continue;            if (vis[tx][ty]) continue;            if (map[tx][ty] == ‘.‘) {                cnt++;                que.push(make_pair(tx,ty));            }            vis[tx][ty] = 1;        }    }    return cnt;}int main(){    int i,j;    while (cin >> n >> m,m+n) {   //m行    n列        for (i = 0; i < m; ++ i)            for (j = 0;j < n ; ++ j) {                cin >> map[i][j];                if (map[i][j] == ‘@‘)                    x = i,y = j;            }            //cout << x << " " << y << endl;            cout << bfs() << endl;    }    return 0;}


DFS：

#include "iostream"#include "cstdio"#include "memory.h"#include "queue"using namespace std;const int MAX = 22;const int dx[] = {1,-1,0,0},dy[] = {0,0,1,-1};char map[MAX][MAX];int vis[MAX][MAX];int x,y;int n,m;int cnt;void dfs(int x,int y){    vis[x][y] = 1;    int i, tx, ty;    for (i = 0;i < 4 ; ++i) {        tx = x + dx[i];        ty = y + dy[i];        if (tx >= 0 && ty >= 0 && tx < m && ty < n && map[tx][ty] != ‘#‘ && !vis[tx][ty]) {                cnt ++;                dfs(tx,ty);        }    }}int main(){    int i,j;    while (cin >> n >> m,m+n) {   //m行    n列        for (i = 0; i < m; ++ i)            for (j = 0;j < n ; ++ j) {                cin >> map[i][j];                if (map[i][j] == ‘@‘)                    x = i,y = j;            }            cnt = 1;            dfs(x,y);            cout << cnt << endl;        memset(vis,0,sizeof(vis));    }    return 0;}

hdu1312