HDU - 1175 连连看

 3 4
1 2 3 4
0 0 0 0
4 3 2 1
4
1 1 3 4
1 1 2 4
1 1 3 3
2 1 2 4
3 4
0 1 4 3
0 2 4 1
0 0 0 0
2
1 1 2 4
1 3 2 3
0 0 

Sample Output

 YES
NO
NO
NO
NO
YES 

思路：带着方向的DFS，回溯找答案

#include <iostream>
#include <cstdio>
#include <cstring>
#include <algorithm>
using namespace std;
const int MAXN = 1010;

struct point{
	int x,y;
	bool operator == (point a){
		return x == a.x && y == a.y;
	}
}s,e;
int map[MAXN][MAXN],n,m,flag;
int vis[MAXN][MAXN];
int dx[4] = {-1,0,1,0};
int dy[4] = {0,1,0,-1};

int dfs(point x,int dir,int num){
	if (flag)
		return 1;
	if (num > 2)
		return 0;
	if (num == 2){
		if ((dir == 0 && x.y != e.y) || (dir == 1 && x.x != e.x) || 
				(dir == 2 && x.y != e.y) || (dir == 3 && x.x != e.x))
			return 0;
	}
	if (x == e){
		flag = true;
		return 1;
	}
	if (x.x < 1 || x.y < 1 || x.x > n || x.y > m || map[x.x][x.y] != 0 || vis[x.x][x.y])
		return 0;
	vis[x.x][x.y] = 1;
	for (int i = 0; i < 4; i++){
		point tmp;
		tmp.x = x.x + dx[i];
		tmp.y = x.y + dy[i];
		if (dir == i)
			dfs(tmp,i,num);
		else dfs(tmp,i,num+1);
	}
	vis[x.x][x.y] = 0;
}

int main(){
	int k;
	while (scanf("%d%d",&n,&m) != EOF && n+m){
		for (int i = 1; i <= n; i++)
			for (int j = 1; j <= m; j++)
				scanf("%d",&map[i][j]);
		scanf("%d",&k);
		while (k--){
			scanf("%d%d%d%d",&s.x,&s.y,&e.x,&e.y);
			if (s == e){
				printf("NO\n");
				continue;
			}
			if (map[s.x][s.y] != map[e.x][e.y]){
				printf("NO\n");
				continue;
			}
			flag = 0;
			if (map[s.x][s.y] == map[e.x][e.y] && map[s.x][s.y] != 0){
				memset(vis,0,sizeof(vis));
				vis[s.x][s.y] = 1;
				for (int i = 0; i < 4; i++){
					point tmp;
					tmp.x = s.x + dx[i];
					tmp.y = s.y + dy[i];
					if (flag == 0)
						dfs(tmp,i,0);
				}
			}
			if (flag)
				printf("YES\n");
			else printf("NO\n");
		}
	}
	return 0;
}

HDU - 1175 连连看,布布扣,bubuko.com

HDU - 1175 连连看

原文：http://blog.csdn.net/u011345136/article/details/21555305