題目鏈接：http://acm.hdu.edu.cn/showproblem.php?pid=1312

-----------------------------------------------------------------------------------

題意：根據地圖,問可以到達多少地方.‘@‘為起點, ‘ . ‘為路,可以到達, ‘ # ‘為墻,不能通過.

思路：DFS，按照一定方式搜索標記。

代碼：

#include<cstdio>
#include<cstring>
#include<algorithm>
#include<iostream>
#include
 
<string>
#include<vector>
#include<stack>
#include<bitset>
#include<cstdlib>
#include<cmath>
#include<set>
#include<list>
#include<deque>
#include<map>
#include<queue>
using namespace std;
typedef long long ll;
const double PI = acos(-1.0
 
);
const double eps = 1e-6;
const int MAXN =20+5;
int H;
int W;
char road[MAXN][MAXN];
int flag[MAXN][MAXN];
int ans =0;

void dfs(int i,int j){
    if(road[i][j+1]==‘.‘&&flag[i][j+1]==0){
        ans++;
        flag[i][j+1]=1;
        dfs(i,j+1);
    }
    if(road[i][j-1]==‘.‘&&flag[i][j-1
 
]==0){
        ans++;
        flag[i][j-1]=1;
        dfs(i,j-1);
    }
    if(road[i+1][j]==‘.‘&&flag[i+1][j]==0){
        ans++;
        flag[i+1][j]=1;
        dfs(i+1,j);
    }
    if(road[i-1][j]==‘.‘&&flag[i-1][j]==0){
        ans++;
        flag[i-1][j]=1;
        dfs(i-1,j);
    }
}

int main(void){
    
    while(~scanf("%d %d",&W,&H)&&(W!=0&&H!=0)){
        ans= 0;
        for(int i=0;i<MAXN;i++){
            for(int j=0;j<MAXN;j++){
                road[i][j]=‘#‘;
                flag[i][j]=0;
            }
        }
        for(int i=0;i<H;i++){
            scanf("%s",&road[i]);
            //printf("road:%s\n",road[i]);
        }
        int inx =0;
        int iny =0;
        for(int i=0;i<H;i++){
            for(int j=0;j<W;j++){
                if(road[i][j]==‘@‘){
                    ans++;
                    inx =i;
                    iny =j;
                    flag[i][j]=1;
                    //printf("%d %d\n",inx,iny);
                }
            }
        }
        dfs(inx,iny);
        printf("%d\n",ans);
    }
    return 0;

}

HDU 1312（DFS_C題）解題報告