poj 2243 Knight Moves

#include<iostream>  
#include<queue>  
#include<cstdio>  
#include<cmath>  
#include<cstdlib>  
#include<cstring>  
using namespace std;  
struct knight{  
    int x,y,step;  
    int g,h,f;  
    bool operator < (const knight &k) const{  
        return f > k.f;  
    }  
}k;  
bool visited[8][8];  
int x2,y2,ans; 
int dir[8][2] = {{-2,-1},{-2,1},{2,-1},{2,1},{-1,-2},{-1,2},{1,-2},{1,2}};  
priority_queue<knight>que;
bool in(const knight &a)  {  
    if(a.x<0||a.y<0||a.x>=8||a.y>= 8)    
        return false;
    return true;  
}  
int Heuristic(const knight &a){
    return (abs(a.x-x2)+abs(a.y-y2))*10;  
}  
void Astar(){  
    knight t,s;  
    while(!que.empty()){  
        t=que.top();  
        que.pop();  
        visited[t.x][t.y] = true;  
        if(t.x==x2&&t.y==y2){  
            ans=t.step;
            break;  
        }  
        for(int i=0;i<8;i++){  
            s.x=t.x+dir[i][0];  
            s.y=t.y+dir[i][1];  
            if(in(s)&&!visited[s.x][s.y]){  
                s.g=t.g+23;
                s.h=Heuristic(s);
                s.f=s.g+s.h;  
                s.step=t.step+1;  
                que.push(s); 
            }  
        }  
    }  
}
int main(){  
    char line[5]; 
    int x1,y1;
    while(gets(line)){  
        x1=line[0]-‘a‘;y1=line[1]-‘1‘;  
        x2=line[3]-‘a‘;y2=line[4]-‘1‘;  
        memset(visited,false,sizeof(visited));  
        k.x=x1;  
        k.y=y1;  
        k.g=k.step=0;  
        k.h=Heuristic(k);  
        k.f=k.g+k.h;  
        while(!que.empty()) que.pop();  
        que.push(k);
        Astar();
        printf("To get from %c%c to %c%c takes %d knight moves.\n",line[0],line[1],line[3],line[4],ans);  
    }  
    return 0;  
}