UVA 439 BFS 骑士的移动

#include<iostream>
#include<cstdio>
#include<string>
#include<string.h>
#include<math.h>
#include<queue>
#include<map>
#include<algorithm>
using namespace std;
int dx,dy;
struct node{
    int step;
    int x;
    int y;
   friend  bool operator <(node a,node b){
        return a.step>b.step;
    }
};
int dir[8][2]={{2,1},{1,2},{-1,2},{-2,1},{-2,-1},{-1,-2},{2,-1},{1,-2}};
priority_queue<node> q;
int  bfs(){

    int s,d;
    while(!q.empty()){
        node temp=q.top();
        q.pop();
        if(dx==temp.x&&dy==temp.y){return temp.step;}
        for(int i=0;i<8;i++){
            s=temp.x+dir[i][0];
            d=temp.y+dir[i][1];
            if(s>0&&s<9&&d>0&&d<9){
                node next;
                next.x=s;
                next.y=d;
                next.step=temp.step+1;
                q.push(next);
            }
        }
    }
    return 0;
}
int main(){
  int a,b,ss;
  char f,g;
  while(cin>>f>>b>>g>>dy){
        a=f-'a'+1;
        dx=g-'a'+1;
        while(!q.empty()) q.pop();
    node n;
    n.x=a;
    n.y=b;
    n.step=0;
    q.push(n);
    ss=bfs();
    printf("To get from %c%d to %c%d takes %d knight moves.\n",f,b,g,dy,ss);
  }


  return 0;
  }