1113.红与黑

dfs

#include <iostream>
#include <cstdio>
#include <algorithm>
using namespace std;
const int N = 30;
char g[N][N];
int n,m;
int dfs(int x,int y)
{
    int res=1;
    int dx[4]={-1,0,1,0},dy[4]={0,1,0,-1};
    g[x][y]='#';
    for (int i=0;i<4;i++)
    {
        int xx=x+dx[i];
        int yy=y+dy[i];
        if (xx>=0&&xx<n&&yy>=0&&yy<m&&g[xx][yy]=='.')
        {
            res+=dfs(xx,yy);
        }
    }
    return res;
}
int main()
{
    while (cin>>m>>n,m||n)
    {
        int a,b;
        for (int i=0;i<n;i++) scanf("%s",g[i]);
        for (int i=0;i<n;i++)
            for (int j=0;j<m;j++)
            {
                if (g[i][j]=='@')
                {
                    a=i,b=j;
                }
            }
        printf("%d\n",dfs(a,b));
    }
    return 0;
}

bfs

#include <iostream>
#include <cstdio>
#include <algorithm>
#include <cstring>
#include <queue>
using namespace std;
typedef pair<int,int> PII;
#define x first
#define y second
const int N = 30;
char g[N][N];
int n,m;
int st[N][N];
void bfs(PII start,int &ans)
{
    queue<PII>q;
    q.push(start);
    st[start.x][start.y]=1;
    while (q.size())
    {
        PII t=q.front();
        q.pop();
        int dx[4]={-1,0,1,0},dy[4]={0,1,0,-1};
        for (int i=0;i<4;i++)
        {
            int x=t.x+dx[i];
            int y=t.y+dy[i];
            if (g[x][y]=='#') continue;
            if (st[x][y]!=-1) continue;
            if (x<0||x>=n||y<0||y>=m) continue;
            ans++;
            st[x][y]=1;
            q.push({x,y});
        }
    }
}
int main()
{
    while (scanf("%d%d",&m,&n),m||n)
    {
        memset(st,-1,sizeof st);  //注意多组数据，一组结束后需要恢复现场
        int ans=1;
        for (int i=0;i<n;i++) scanf("%s",g[i]);
        PII start; 
        for (int i=0;i<n;i++)
            for (int j=0;j<m;j++)
            {

                if (g[i][j]=='@')
                {
                     start={i,j};
                }
            }
        bfs(start,ans);
        printf("%d\n",ans);
    }
    return 0;
}