广搜bfs

来源：https://www.luogu.org/problemnew/show/P1443

错误：x1<=n || y1<=n  

emmmmmmmmmmm...... 我也不想说啥了。。。

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

using namespace std;

struct node
{
	int x,y;
};

const int maxSize=400;
int n,m;
int a[maxSize+5][maxSize+5];
queue <node> q;
int fx[8][2]={{2,1},{1,2},{-2,1},{-1,2},{2,-1},{1,-2},{-2,-1},{-1,-2}};

void bfs()
{
	int i,j,x,y,x1,y1;
	node n1,n2;
	
	while (!q.empty())
	{
		n1=q.front();
		q.pop();
		x=n1.x;		y=n1.y;
		
		for (i=0;i<8;i++)
		{
			x1=x+fx[i][0];
			y1=y+fx[i][1];
			if (x1<0 || y1<0 || x1>=n || y1>=m)
				continue;
			if (a[x1][y1]==-1 || a[x1][y1]>a[x][y]+1)
			{
				n2.x=x1;	n2.y=y1;
				q.push(n2);		
				a[x1][y1]=a[x][y]+1;
			}				
		}
	}
	for (i=0;i<n;i++)
	{
		for (j=0;j<m;j++)
			printf("%-5d",a[i][j]);
		printf("\n");
	}
}

int main()
{
	int x,y,i,j;
	node n1;
	
	freopen("a.txt","r",stdin);
	
	scanf("%d%d%d%d",&n,&m,&x,&y);
	
	for (i=0;i<n;i++)
		for (j=0;j<m;j++)
			a[i][j]=-1;
			
	n1.x=x-1;		n1.y=y-1;
	a[x-1][y-1]=0;
	
	q.push(n1);
	bfs();
	
	
	return 0;
}