HDOJ 2952 Counting Sheep

题目链接:http://acm.hdu.edu.cn/showproblem.php?pid=2952

Counting Sheep

Time Limit: 2000/1000 MS (Java/Others)    Memory Limit: 32768/32768 K (Java/Others)
Total Submission(s): 2231    Accepted Submission(s): 1474

Problem Description

A while ago I had trouble sleeping. I used to lie awake, staring at the ceiling, for hours and hours. Then one day my grandmother suggested I tried counting sheep after I'd gone to bed. As always when my grandmother suggests things, I decided to try it out. The only problem was, there were no sheep around to be counted when I went to bed.


Creative as I am, that wasn't going to stop me. I sat down and wrote a computer program that made a grid of characters, where # represents a sheep, while . is grass (or whatever you like, just not sheep). To make the counting a little more interesting, I also decided I wanted to count flocks of sheep instead of single sheep. Two sheep are in the same flock if they share a common side (up, down, right or left). Also, if sheep A is in the same flock as sheep B, and sheep B is in the same flock as sheep C, then sheeps A and C are in the same flock.


Now, I've got a new problem. Though counting these sheep actually helps me fall asleep, I find that it is extremely boring. To solve this, I've decided I need another computer program that does the counting for me. Then I'll be able to just start both these programs before I go to bed, and I'll sleep tight until the morning without any disturbances. I need you to write this program for me.

 

Input

The first line of input contains a single number T, the number of test cases to follow.

Each test case begins with a line containing two numbers, H and W, the height and width of the sheep grid. Then follows H lines, each containing W characters (either # or .), describing that part of the grid.

 

Output

For each test case, output a line containing a single number, the amount of sheep flock son that grid according to the rules stated in the problem description.

Notes and Constraints
0 < T <= 100
0 < H,W <= 100

 

Sample Input

24 4#.#..#.##.##.#.#3 5###.#..#..#.###

 

Sample Output

63

 

Source

IDI Open 2009

 

题意:给你一个图，算出有都少个“#”快。

题解:递归标记一些就好了....DFS都不用回溯。

AC代码:

#include<iostream>#include<string>#define N 105using namespace std;string str[N];int t,m,n;int dir[][2]={    {0,1},{0,-1},{1,0},{-1,0}};void dfs(int x,int y ){    for(int i=0;i<4;i++){        int dx=x+dir[i][0],dy=y+dir[i][1];        if(dx>=0&&dx<m&&dy>=0&&dy<n&&str[dx][dy]=='#'){            str[dx][dy]='.';            dfs(dx,dy);        }    }}int main(){    cin.sync_with_stdio(false);    cin>>t;    while(t--){        int sum=0;        cin>>m>>n;        for(int i=0;i<m;i++)cin>>str[i];        for(int i=0;i<m;i++)            for(int j=0;j<n;j++)            if(str[i][j]=='#'){            sum++;            str[i][j]='.';            dfs(i,j);        }        cout<<sum<<endl;    }    return 0;}