hdu1175(连连看）

#include <iostream>
#include <cstdio>
#include <cstring>

using namespace std;
const int maxn = 1010;
const int INF = 5;

int n = 0, m = 0, q = 0;
int map[maxn][maxn];
int x1=0, y1=0, x2=0, y2=0;
int dr[4][2] = {{0, 1}, {0, -1}, {-1, 0}, {1, 0}};
//                 E       W       N          S
int h = 0, w = 0;
typedef struct node {
    int x;
    int y;
    int dir;//记录走的方向
    int tn;//记录转弯次数
}node;
node list[maxn*maxn], E;
int turn[maxn][maxn]; //到达此位置用的最小转弯次数

bool valid(int x, int y) {
    if (x<=0 || x>n || y<=0 || y>m) { return false;} //在图中
    if (!(0==map[x][y] || (x==x2&&y==y2))) { return false;} //走0或到达终点
    return true;
}

int expand(node& R) {   //引用
    for (int i = 0; i < 4; i++) {
        E.x = R.x+dr[i][0];
        E.y = R.y+dr[i][1];
        E.dir = i;
        if (valid(E.x, E.y)) { //剪枝1, 2
            if (E.dir != R.dir) {
                E.tn = R.tn+1;
            }
            else {
                E.tn = R.tn;
            }
            if (E.tn<turn[E.x][E.y] && E.tn<3) { //剪枝3, 4转弯次数小于3, 小于已经可达此处的最小转弯次数
                if (E.x==x2 && E.y==y2) {
                    return 1;
                }
                turn[E.x][E.y] = E.tn; //更新
                w++;
                list[w] = E;//入队
            }
        }
    }
    return 0;
}

bool work() {
    for (int i = 0; i<=n; i++) {
        for (int j=0; j<=m; j++) {
            turn[i][j]=INF;
        }
    }
    if (map[x1][y1] != map[x2][y2]) { return false;}
    if (0==map[x1][y1] || 0==map[x2][y2]) { return false;}
    //if (!valid(x1, y1) || !valid(x2, y2)) { return false;}
    h = 0, w = 0;//队列的两个指针
    w++;
    list[w].x = x1;
    list[w].y = y1;
    list[w].tn = -1;
    list[w].dir = -1;
    turn[x1][y1] = 0;
    while (h < w) {
        h++;
        if (list[h].x==x2 && list[h].y==y2) {
            return true;
        }
        if (expand(list[h])) {
            return true;
        }
    }
    return false;
}

int init() {
    for (int i = 1; i <= n; i++) {
        for (int j = 1; j <= m; j++) {
            scanf("%d", &map[i][j]);
        }
    }
    scanf("%d", &q);
    for (int i = 0; i < q; i++) {
        scanf("%d%d%d%d", &x1, &y1, &x2, &y2);
        if (work()) {
            printf("YES\n");
        }
        else {
            printf("NO\n");
        }
    }
    return 0;
}

int main()
{
    while (2 == scanf("%d%d", &n, &m) && m+n) {
        init();
    }
    return 0;
}