P1126 机器人搬重物

题目地址：https://www.luogu.org/problem/P1126

看着机房孙哥再做这个题，我也尝试一波，没想到卡了这么长时间，总结一下，这题细节超多，一开始写了个有返回值的bfs，wa，还得注意转向的问题，走一步，两步，三步都是一秒，还有对初始坐标点的处理。。。

代码：

#include<cstdio>
#include<cstring>
#include<queue>
#include<cmath>
using namespace std;
const int inf=0x3f3f3f3f;
const int maxn=50+10;
struct Node 
{
	int x;
	int y;
	int time;
	char dir;
};
int n,m,sx,sy,fx,fy,a[maxn][maxn],dis[4][2]={0,1,1,0,0,-1,-1,0};
int vis[maxn][maxn];
char c,s[4]={'S','W','N','E'};
queue<Node> q;
bool judge(int x,int y)
{
	bool error=false;
	if(a[x][y]==0&&x>=1&&y>=1&&x<n&&y<m&&a[x-1][y-1]==0&&a[x-1][y]==0&&a[x][y-1]==0)
	{
		error=false;
	}
	else error=true;
	if(error==true)
	return false;     	
	else 
	return true;
}
void bfs()
{
	while(!q.empty())
	{
		Node now=q.front();
		q.pop();
		char to=now.dir;
		int num;
		for(int i=0;i<4;i++)
		{
			if(s[i]==to) 
			num=i;
		}
		for(int i=0;i<4;i++)
		{
			int k=fabs(i-num),tx=now.x,ty=now.y,walk_2=0,walk_3=0;
			if(k==3) k=1;
			else if(k==2) k=2;
			else if(k==1) k=1;
			else if(k==0) k=0;
			if(i==0)tx++;
			if(i==1)ty--;
			if(i==2)tx--;
			if(i==3)ty++;
			if(judge(tx,ty))
			{	
				walk_2=1;
				if(vis[tx][ty]>now.time+k+1)
				{
					q.push({tx,ty,now.time+k+1,s[i]});
					vis[tx][ty]=now.time+k+1;
				}
			}
			if(walk_2==1)
			{
				if(i==0)tx++;
				if(i==1)ty--;
				if(i==2)tx--;
				if(i==3)ty++;
				if(judge(tx,ty))
				{
					walk_3=1;
					if(vis[tx][ty]>now.time+k+1)
					{
						q.push({tx,ty,now.time+k+1,s[i]});
						vis[tx][ty]=now.time+k+1;
					}	
				}
			}
			if(walk_3==1)
			{	
				if(i==0)tx++;
				if(i==1)ty--;
				if(i==2)tx--;
				if(i==3)ty++;
				if(judge(tx,ty))
				{
					if(vis[tx][ty]>now.time+k+1)
					{
						q.push({tx,ty,now.time+k+1,s[i]});
						vis[tx][ty]=now.time+k+1;
					}
				}
			}			
		}
	}
}
int main()
{
	memset(vis,inf,sizeof vis);
	scanf("%d %d",&n,&m);
	for(int i=0;i<n;i++)
	for(int j=0;j<m;j++)
	scanf("%d",&a[i][j]);
	scanf("%d %d %d %d %c",&sx,&sy,&fx,&fy,&c);
	q.push({sx,sy,0,c});
	vis[sx][sy]=0;
	bfs(); 
	if(vis[fx][fy]==inf)
		printf("-1\n");
	else 
		printf("%d",vis[fx][fy]);
	return 0;
}