hdu 1312 Red and Black

骑猪看日落 2022-05-31 09:10 119阅读 0赞

# Red and Black #

**Time Limit: 2000/1000 MS (Java/Others) Memory Limit: 65536/32768 K (Java/Others)  
Total Submission(s): 23509 Accepted Submission(s): 14218**

Problem Description

There is a rectangular room, covered with square tiles. Each tile is colored either red or black. A man is standing on a black tile. From a tile, he can move to one of four adjacent tiles. But he can't move on red tiles, he can move only on black tiles.  
  
Write a program to count the number of black tiles which he can reach by repeating the moves described above.

Input

The input consists of multiple data sets. A data set starts with a line containing two positive integers W and H; W and H are the numbers of tiles in the x- and y- directions, respectively. W and H are not more than 20.  
  
There are H more lines in the data set, each of which includes W characters. Each character represents the color of a tile as follows.  
  
'.' - a black tile  
'\#' - a red tile  
'@' - a man on a black tile(appears exactly once in a data set)

Output

For each data set, your program should output a line which contains the number of tiles he can reach from the initial tile (including itself).

Sample Input

6 9 ....\#. .....\# ...... ...... ...... ...... ...... \#@...\# .\#..\#. 11 9 .\#......... .\#.\#\#\#\#\#\#\#. .\#.\#.....\#. .\#.\#.\#\#\#.\#. .\#.\#..@\#.\#. .\#.\#\#\#\#\#.\#. .\#.......\#. .\#\#\#\#\#\#\#\#\#. ........... 11 6 ..\#..\#..\#.. ..\#..\#..\#.. ..\#..\#..\#\#\# ..\#..\#..\#@. ..\#..\#..\#.. ..\#..\#..\#.. 7 7 ..\#.\#.. ..\#.\#.. \#\#\#.\#\#\# ...@... \#\#\#.\#\#\# ..\#.\#.. ..\#.\#.. 0 0

Sample Output

45 59 6 13

Source

[Asia 2004, Ehime (Japan), Japan Domestic][Asia 2004_ Ehime _Japan_ Japan Domestic]

题目大意：  
题目的要求就是从'@'开始，只能走'.',问可以走多少步，也就是说有多少个'.'相连。  
题目解析：  
这个题目就是非常简单的dfs题目，就是一个模板题目，直接遍历一遍即可AC，非常水

代码：

#include <bits/stdc++.h>
    using namespace std;
    const int maxn = 1e3;
    char mapp[maxn][maxn];
    int vis[maxn][maxn];
    int ans;
    int dir[4][2]= {
       {0,1},{0,-1},{1,0},{-1,0}};
    int l,c;
    int check(int x,int y)
    {
        if(x<0||y<0||x>=c||y>=l||vis[x][y]||mapp[x][y]!='.')
            return 1;
        else
            return 0;
    
    }
    void dfs(int x,int y)
    {
        vis[x][y] = 1;
        for(int i=0; i<4; i++)
        {
            int a = x+dir[i][0];
            int b = y+dir[i][1];
            if(!check(a,b))
            {
                ans++;
                dfs(a,b);
            }
        }
    }
    int main()
    {
        //freopen("in.txt","r",stdin);
        while(cin>>l>>c&&(c||l))
        {
            int a,b;
            ans = 1;
            memset(vis,0,sizeof(vis));
            for(int i=0; i<c; i++)
                for(int j=0; j<l; j++)
                {
                    cin>>mapp[i][j];
                    if(mapp[i][j]=='@')
                    {
                        a = i;
                        b = j;
                    }
                }
            dfs(a,b);
            cout<<ans<<endl;
        }
        return 0;
    }

[Asia 2004_ Ehime _Japan_ Japan Domestic]: http://acm.hdu.edu.cn/search.php?field=problem&key=Asia+2004%2C+Ehime+%28Japan%29%2C+Japan+Domestic&source=1&searchmode=source