ZOJ 4020 Traffic Light（BFS+vector、queue应用）

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题目链接：http://acm.zju.edu.cn/onlinejudge/showProblem.do?problemId=5748

#include <iostream>
#include <cstdio>
#include <cstring>
#include <cmath>
#include <vector>
#include <queue>
#include <algorithm>
using namespace std;

struct node{
	int x, y, d;
};
vector<int> a[100010], vis[100010];
int sx, sy, ex, ey, n, m;
int nextx[4]={0,0,1,-1};
int nexty[4]={1,-1,0,0};
int check(int x, int y)
{
	if (x>0 && x<=n && y>0 && y<=m && vis[x][y]==0)
		return 1;
	return 0;
}

int bfs()
{
	queue<node> que;
	vis[sx][sy] = 1;
	node start;
	start.d=0;
	start.x=sx;
	start.y=sy;
	que.push(start);
	while(que.size())
	{
		start=que.front();
		que.pop();
		int x=start.x,y=start.y; 
	    int state=a[x][y];
	    if(start.d%2)
	    {
	    	if(state)
	    	   state=0;
	    	else
	    	    state=1;
		}
		if (state == 0)
		{
			node t;
			for(int i=2;i<4;i++)
			{
				t.x=x+nextx[i];
				t.y=y+nexty[i];
				t.d=start.d+1;
				if(t.x== ex&& t.y==ey)
	               return t.d;
				if(check(t.x,t.y))
				{
					vis[t.x][t.y] = 1;
			        que.push(t);
				}
			}
		}
		else
		{
			node t;
			for(int i=0;i<2;i++)
			{
				t.x=x+nextx[i];
				t.y=y+nexty[i];
				t.d=start.d+1;
				if(t.x== ex&& t.y==ey)
	               return t.d;
				if(check(t.x,t.y))
				{
					vis[t.x][t.y] = 1;
			        que.push(t);
				}
			}
		}
    }
    return -1;
}
int main()
{
	int t;
	scanf("%d", &t); 
	while (t--)
	{
		scanf("%d%d", &n, &m);
		for(int i=1;i<=n;i++){
		   	a[i].clear();
		   	vis[i].clear();
		   	a[i].push_back(0);
		   	vis[i].push_back(0);
		}
		for (int i = 1; i <= n; i++)
			for (int j = 1; j <= m; j++)
			{
				int x;
				cin>>x;
				a[i].push_back(x);
				vis[i].push_back(0);	
			}
 
		scanf("%d%d%d%d", &sx, &sy, &ex, &ey);
		if(sx==ex&&sy==ey)
			printf("0\n");
		else	
		    printf("%d\n", bfs());
	}
	return 0;
}