POJ 1979 dfs和bfs两种解法

 

fengyun@fengyun-server:~/learn/acm/poj$ cat 1979.cpp
#include<cstdio>
#include<iostream>
#include<string>
#include<algorithm>
#include<iterator>
#include<sstream>//istringstream
#include<cstring>
#include<queue>

using namespace std;

char map[21][21];
char visited[21][21];
int w, h;
int ans;

void dfs(int i, int j)
{
   if(i<0||i>=h||j<0||j>=w)
       return;
   if(map[i][j]=='#')
       return;
   if(map[i][j]=='.'&&visited[i][j]==0)
   {
        ans++;
        visited[i][j]=1;
        dfs(i-1,j);
        dfs(i+1,j);
        dfs(i,j+1);
        dfs(i,j-1);
   }

}

int dir[4][2]={
    {-1, 0},
    {1, 0},
    {0, 1},
    {0, -1},
};
void bfs(int i, int j)
{
    queue<int> q;
    q.push(i*w+j);
    visited[i][j]=1;

    while(!q.empty())
    {
        //pop
        //add neighbors
        int ni,nj;
        ni=q.front()/w;
        nj=q.front()%w;
        q.pop();
        ans++;
        for(int k=0;k<4;k++)
        {
            int row=ni+dir[k][0];
            int col=nj+dir[k][1];
            if(row>=0&&row<h&&col>=0&&col<w&&map[row][col]=='.'&&visited[row][col]==0)
            {
                visited[row][col]=1;
                q.push(row*w+col);
            }
           
        }
       
    }

}

int main()
{
    while(cin>>w>>h && (w||h))
    {
        int x, y;
        memset(visited, 0, sizeof(visited));
        ans=0;
        for(int i=0;i<h;i++)
        {
            for(int j=0;j<w;j++)
            {
                cin>>map[i][j];
                if(map[i][j]=='@')
                {
                    x=i;
                    y=j;
                    map[i][j]='.';
                }
            }
        }

        //dfs(x,y);
        bfs(x,y);
        cout<<ans<<endl;
    }

    return 0;
}