【HDU1198】Farm Irrigation（回溯+记忆化搜索）

数据流小，深搜即可。有些暴力。看其他人的题解用二维转换成一维做的并查集很巧妙，马上去研究一下！！

#include <iostream>
#include <cstring>
#include <cstdlib>
#include <cstdio>
#include <cmath>
#include <cctype>
#include <algorithm>
#include <numeric>
#include <string>
#include <limits.h>
#include <map>
using namespace std;

int m, n, ans = 0;
char Map[55][55];
bool vis[55][55];
map<char, string> check;

void dfs (int x, int y) {

    vis[x][y] = 1;

    if (check[Map[x][y]].find("U") != -1 && check[Map[x - 1][y]].find("D") != -1) {
        if (!vis[x - 1][y]) dfs (x - 1, y);
    }

    if (check[Map[x][y]].find("D") != -1 && check[Map[x + 1][y]].find("U") != -1) {
        if (!vis[x + 1][y]) dfs (x + 1, y);
    }

    if (check[Map[x][y]].find("L") != -1 && check[Map[x][y - 1]].find("R") != -1) {
        if (!vis[x][y - 1]) dfs (x, y - 1);
    }

    if (check[Map[x][y]].find("R") != -1 && check[Map[x][y + 1]].find("L") != -1) {
        if (!vis[x][y + 1]) dfs (x, y + 1);
    }
}

int main () {

    check['A'] = "UL";  check['B'] = "UR";  check['C'] = "DL";
    check['D'] = "DR";  check['E'] = "UD";  check['F'] = "LR";
    check['G'] = "ULR"; check['H'] = "UDL"; check['I'] = "DLR";
    check['J'] = "UDR"; check['K'] = "UDLR";

    while (~scanf("%d%d", &m, &n)) {
        if (m < 0 && n < 0) {
            break;
        }
        memset (vis, 0, sizeof(vis));
        memset (Map, 0, sizeof(Map));
        for (int i = 0; i < m ; ++ i) {
            for (int j = 0 ; j < n; ++ j) {
                cin >> Map[i][j];
            }
        }
        ans = 0;
        for (int i = 0; i < m; ++ i) {
            for (int j = 0; j < n; ++j) {
                if (vis[i][j] != 1) {
                    dfs (i, j);
                    ans ++;
                }
            }
        }

        cout << ans << endl;
    }
    return 0;
}