ZOJ 2412 Farm Irrigation(DFS 条件连通块)

标签：acm   王桂平   图论   

题意  两块农田里面的管道可以直接连接的话  他们就可以共用一个水源   有11种农田  上面的管道位置是一定的  给你一个农田矩阵  问至少需要多少水源

DFS的连通块问题  两个相邻农田的管道可以直接连接的话他们就属于一个连通块  题目就是求连通块个数 

#include<cstdio>
#include<cstring>
using namespace std;
const int N = 55;
char mat[N][N];
int type[11][4] = {   //对应11种水管类型 按顺时针方向有管道的为1否则为0
    {1, 0, 0, 1}, {1, 1, 0, 0}, {0, 0, 1, 1}, {0, 1, 1, 0},
    {1, 0, 1, 0}, {0, 1, 0, 1}, {1, 1, 0, 1}, {1, 0, 1, 1},
    {0, 1, 1, 1}, {1, 1, 1, 0}, {1, 1, 1, 1}
};

int dfs(int r, int c)
{
    int cur = mat[r][c] - 'A';
    if(cur < 0 || cur > 10) return 0;
    mat[r][c] = 0;           //标记已经访问 0-'A'是小于0的
    int up = mat[r - 1][c] - 'A', dw = mat[r + 1][c] - 'A',
        le = mat[r][c - 1] - 'A', ri = mat[r][c + 1] - 'A';  //4个相邻块的管道类型
    if(up > -1 && up < 11 && type[up][2] && type[cur][0])  dfs(r - 1, c);
    if(dw > -1 && dw < 11 && type[dw][0] && type[cur][2])  dfs(r + 1, c);
    if(le > -1 && le < 11 && type[le][1] && type[cur][3])  dfs(r, c - 1);
    if(ri > -1 && ri < 11 && type[ri][3] && type[cur][1])  dfs(r, c + 1);
    return 1;     //一个连通块中只有一个返回1
}

int main()
{
    int n, m, ans;
    while (scanf("%d%d", &n, &m), n >= 0)
    {
        ans = 0;
        memset(mat, 0, sizeof(mat));
        for(int i = 1; i <= n; ++i)
            scanf("%s", mat[i] + 1);
        for(int i = 1; i <= n; ++i)
            for(int j = 1; j <= m; ++j)
                ans += dfs(i, j);
        printf("%d\n", ans);
    }
    return 0;
}

Benny has a spacious farm land to irrigate. The farm land is a rectangle, and is divided into a lot of samll squares. Water pipes are placed in these squares. Different square has a different type of pipe. There are 11 types of pipes, which is marked from A to K, as Figure 1 shows.

Figure 1

Benny has a map of his farm, which is an array of marks denoting the distribution of water pipes over the whole farm. For example, if he has a map

ADC
FJK
IHE

Figure 2

Several wellsprings are found in the center of some squares, so water can flow along the pipes from one square to another. If water flow crosses one square, the whole farm land in this square is irrigated and will have a good harvest in autumn.

Now Benny wants to know at least how many wellsprings should be found to have the whole farm land irrigated. Can you help him?

Note: In the above example, at least 3 wellsprings are needed, as those red points in Figure 2 show.

There are several test cases! In each test case, the first line contains 2 integers M and N, then M lines follow. In each of these lines, there are N characters, in the range of ‘A‘ to ‘K‘, denoting the type of water pipe over the corresponding square. A negative M or N denotes the end of input, else you can assume 1 <= M, N <= 50.

Output

For each test case, output in one line the least number of wellsprings needed.

Sample Input

2 2
DK
HF

3 3
ADC
FJK
IHE

-1 -1

2
3

ZOJ 2412 Farm Irrigation(DFS 条件连通块)

标签：acm   王桂平   图论   

原文地址：http://blog.csdn.net/acvay/article/details/40040181