俩月前写的普通BFS

#include <cstdio>
#include <iostream>
#include <cstring>
#include <queue>
using namespace std;
int CAS,sx,sy,k,ex,ey,vis[305][305],xx[]={1,-1,2,-2,1,-1,2,-2},yy[]={2,-2,1,-1,-2,2,-1,1};
bool check(int x,int y)
{return x>=0&&x<k&&y>=0&&y<k;
}
int bfs()
{queue <int> p,q;p.push(sx),q.push(sy);while(!p.empty()){int tempx=p.front(),tempy=q.front();p.pop();q.pop();if(tempx==ex&&tempy==ey) return vis[ex][ey];for(int i=0;i<=7;i++){if(!vis[tempx+xx[i]][tempy+yy[i]]&&check(tempx+xx[i],tempy+yy[i])){vis[tempx+xx[i]][tempy+yy[i]]=vis[tempx][tempy]+1;p.push(tempx+xx[i]),q.push(tempy+yy[i]);}}}
}
int main()
{scanf("%d",&CAS);for(int ii=1;ii<=CAS;ii++){memset(vis,0,sizeof(vis));scanf("%d%d%d%d%d",&k,&sx,&sy,&ex,&ey);cout<<bfs()<<endl;}
} 

双向搜索（自己yy的。。。随便搞一搞就AC了 我也不知道为什么。。）：

#include <queue>
#include <cstdio>
#include <cstring>
#include <algorithm>
using namespace std;
int cases,dx,dy,k,sx,sy,ex,ey,xx[]={2,2,-2,-2,1,1,-1,-1},yy[]={1,-1,1,-1,2,-2,2,-2},vis[305][305],v[305][305];
queue<pair<int,int> >q;
pair<int,int>p;
int bfs(){while(!q.empty()){p=q.front();q.pop();if(vis[p.first][p.second]==1)for(int i=0;i<=7;i++){dx=p.first+xx[i],dy=p.second+yy[i];if(!vis[dx][dy]&&dx>=0&&dx<k&&dy>=0&&dy<k)v[dx][dy]=v[p.first][p.second]+1,vis[dx][dy]=1,q.push(make_pair(dx,dy));else if(vis[dx][dy]==2)return v[dx][dy]+v[p.first][p.second];}else if(vis[p.first][p.second]==2)for(int i=0;i<=7;i++){dx=p.first+xx[i],dy=p.second+yy[i];if(!vis[dx][dy]&&dx>=0&&dx<k&&dy>=0&&dy<k)v[dx][dy]=v[p.first][p.second]+1,vis[dx][dy]=2,q.push(make_pair(dx,dy));else if(vis[dx][dy]==1)return v[dx][dy]+v[p.first][p.second];}}
}
int main()
{scanf("%d",&cases);for(int ii=1;ii<=cases;ii++){memset(vis,0,sizeof(vis));memset(v,0,sizeof(v));scanf("%d%d%d%d%d",&k,&sx,&sy,&ex,&ey);q.push(make_pair(sx,sy)),q.push(make_pair(ex,ey));vis[sx][sy]=v[sx][sy]=1;vis[ex][ey]=2;if(sx==ex&&sy==ey){printf("0\n");continue;}printf("%d\n",bfs());while(!q.empty())q.pop();}
}