【搜索】【the first editoral】OpenJudge 我是最快的马

#include<cstdio>
#include<queue>
#include<stack>
#include<iostream>
using namespace std;
int G[18][18];
int dx[]= {-2,-2,2,2,-1,1,-1,1};
int dy[]= {-1,1,-1,1,-2,-2,2,2};
int method=0;
struct Point
{
    int x,y;
    int fa;
    int self;
    Point(){}
    Point(int _x,int _y,int _fa,int _self):x(_x),y(_y),fa(_fa),self(_self){}
    bool operator==(Point &tp)
    {
        if(tp.x==x&&tp.y==y)
            return true;
        return false;
    }
}P[150];
int cnt=0;
int bfs(Point start,Point &endz)
{
    queue<Point> q;
    q.push(start);
    G[start.x][start.y]=1;
    int step=0;
    while(!q.empty())
    {
        step++;
        int size=q.size();
        while(size--)
        {
            Point now=q.front();
//            cout<<now.x<<" "<<now.y<<" "<<now.fa<<" "<<now.self<<endl;
            q.pop();
            for(int i=0; i<8; i++)
            {
                int nx=now.x+dx[i];
                int ny=now.y+dy[i];
                int mx=now.x+dx[i]/2;
                int my=now.y+dy[i]/2;
                                                        //  the point visited was flag and be seeing as the the 蹩马脚！！
                if(nx>=0&&nx<=10&&ny>=0&&ny<=10&&G[mx][my]!=2&&!G[nx][ny])
                {
//                    cout<<nx<<" "<<ny<<endl;
                    G[nx][ny]=1;//the cnt is starting from 2,but the P[2] is empty.
                    P[cnt]=Point(nx,ny,now.self,cnt);
                    cnt++;
                    if(P[cnt-1]==endz)
                    {
                        G[nx][ny]=0;
                        endz.fa=P[cnt-1].fa;
                        method++;
                    }
                    else q.push(P[cnt-1]);
                }
            }
        }
        if(method>0) return step;
    }
}
int main()
{
    freopen("a.txt","r",stdin);
    int x,y;
    scanf("%d%d",&x,&y);
    P[cnt++]=Point(x,y,0,0);
    scanf("%d%d",&x,&y);
    P[cnt++]=Point(x,y,-1,1);
    int M;
    scanf("%d",&M);
    for(int i=0; i<M; i++)
    {
        scanf("%d%d",&x,&y);
        G[x][y]=2;
    }
    if(P[0]==P[1])
        {printf("0\n");return 0;}
    int step=bfs(P[0],P[1]);
    stack<Point> st;
    st.push(P[1]);
    int tot=P[1].fa;
    while(1)
    {
        st.push(P[tot]);
//        cout<<P[tot].x<<" "<<P[tot].y<<" "<<P[tot].fa<<endl;
        if(P[tot]==P[0]) break;
        tot=P[tot].fa;
    }

    if(method==1)
    {
        while(!st.empty())
        {
            printf("(%d,%d)",st.top().x,st.top().y);
            st.pop();
            if(st.size()!=0)
                printf("-");
        }
        printf("\n");
    }
    else
    {
        printf("%d\n",step);
    }
}