HDU1401（双向BFS）

题意：http://acm.hdu.edu.cn/showproblem.php?pid=1401

给你8*8的棋盘和4个棋子初始位置、最终位置，问你能否在8次操作后达到该状态。

思路：

双向BFS，起点开始正搜4步，终点倒搜4步，map标记。

 #define IOS ios_base::sync_with_stdio(0); cin.tie(0);
 #include <cstdio>//sprintf islower isupper
 #include <cstdlib>//malloc  exit strcat itoa system("cls")
 #include <iostream>//pair
 #include <fstream>//freopen("C:\\Users\\13606\\Desktop\\Input.txt","r",stdin);
 #include <bitset>
 //#include <map>
 #include<unordered_map>
 #include <vector>
 #include <stack>
 #include <set>
 #include <string.h>//strstr substr strcat
 #include <string>
 #include <time.h>// srand(((unsigned)time(NULL))); Seed n=rand()%10 - 0~9;
 #include <cmath>
 #include <deque>
 #include <queue>//priority_queue<int, vector<int>, greater<int> > q;//less
 #include <vector>//emplace_back
 //#include <math.h>
 #include <cassert>
 #include <iomanip>
 //#include <windows.h>//reverse(a,a+len);// ~ ! ~ ! floor
 #include <algorithm>//sort + unique : sz=unique(b+1,b+n+1)-(b+1);+nth_element(first, nth, last, compare)
 using namespace std;//next_permutation(a+1,a+1+n);//prev_permutation
 //******************
 clock_t __START,__END;
 double __TOTALTIME;
 void _MS(){__START=clock();}
 void _ME(){__END=clock();__TOTALTIME=(double)(__END-__START)/CLOCKS_PER_SEC;cout<<"Time: "<<__TOTALTIME<<" s"<<endl;}
 //***********************
 #define rint register int
 #define fo(a,b,c) for(rint a=b;a<=c;++a)
 #define fr(a,b,c) for(rint a=b;a>=c;--a)
 #define mem(a,b) memset(a,b,sizeof(a))
 #define pr printf
 #define sc scanf
 #define ls rt<<1
 #define rs rt<<1|1
 typedef pair<int,int> PII;
 typedef vector<int> VI;
 typedef unsigned long long ull;
 typedef long long ll;
 typedef double db;
 const double E=2.718281828;
 const double PI=acos(-1.0);
 const ll INF=(1LL<<);
 const int inf=(<<);
 const double ESP=1e-;
 const int mod=(int)1e9+;
 const int N=(int)1e6+;
 
 int mp[][];
 unordered_map<ull,bool>mark;
 struct node
 {
     ull id;
     int step;
 };
 ull get()
 {
     ull now=,temp=;
     int cnt=-;
     for(int i=;i<=;++i)
     {
         for(int j=;j<=;++j)
         {
             ++cnt;
             if(mp[i][j])
                 now|=temp<<cnt;
         }
     }
     return now;
 }
 bool ok(int x,int y)
 {
     return x>=&&x<=&&y>=&&y<=;
 }
 bool ans;
 void bfs(ull start,bool f)
 {
     queue<node>q;
     q.push({start,});
     while(!q.empty())
     {
         node now=q.front();q.pop();
         if(!f)
         {
             if(mark[now.id])continue;
             mark[now.id]=;
         }
         else
         {
             if(mark[now.id])
             {
                 ans=;
                 return;
             }
         }
         if(now.step==)continue;
         int cnt=-;
         for(int i=;i<=;++i)
         {
             for(int j=;j<=;++j)
             {
                 ++cnt;
                 mp[i][j]=(int)(now.id>>cnt)&;
             }
         }
         for(int i=;i<=;++i)
         {
             for(int j=;j<=;++j)
             {
                 if(mp[i][j]&&ok(i-,j)&&mp[i-][j]==&&ok(i-,j)&&mp[i-][j]==)
                 {
                     mp[i-][j]=,mp[i][j]=;
                     q.push({get(),now.step+});
                     mp[i-][j]=,mp[i][j]=;
                 }
                 if(mp[i][j]&&ok(i+,j)&&mp[i+][j]==&&ok(i+,j)&&mp[i+][j]==)
                 {
                     mp[i+][j]=,mp[i][j]=;
                     q.push({get(),now.step+});
                     mp[i+][j]=,mp[i][j]=;
                 }
                 if(mp[i][j]&&ok(i,j-)&&mp[i][j-]==&&ok(i,j-)&&mp[i][j-]==)
                 {
                     mp[i][j-]=,mp[i][j]=;
                     q.push({get(),now.step+});
                     mp[i][j-]=,mp[i][j]=;
                 }
                 if(mp[i][j]&&ok(i,j+)&&mp[i][j+]==&&ok(i,j+)&&mp[i][j+]==)
                 {
                     mp[i][j+]=,mp[i][j]=;
                     q.push({get(),now.step+});
                     mp[i][j+]=,mp[i][j]=;
                 }
                 //--------------------------------------------------------------
                 if(mp[i][j]==&&ok(i-,j)&&mp[i-][j]==)
                 {
                     mp[i-][j]=,mp[i][j]=;
                     q.push({get(),now.step+});
                     mp[i-][j]=;mp[i][j]=;
                 }
                 if(mp[i][j]==&&ok(i+,j)&&mp[i+][j]==)
                 {
                     mp[i+][j]=,mp[i][j]=;
                     q.push({get(),now.step+});
                     mp[i+][j]=;mp[i][j]=;
                 }
                 if(mp[i][j]==&&ok(i,j-)&&mp[i][j-]==)
                 {
                     mp[i][j-]=,mp[i][j]=;
                     q.push({get(),now.step+});
                     mp[i][j-]=;mp[i][j]=;
                 }
                 if(mp[i][j]==&&ok(i,j+)&&mp[i][j+]==)
                 {
                     mp[i][j+]=,mp[i][j]=;
                     q.push({get(),now.step+});
                     mp[i][j+]=;mp[i][j]=;
                 }
             }
         }
     }
 }
 
 int main()
 {
     int x,y;
     while(~sc("%d%d",&x,&y))
     {
         ans=;
         mark.clear();
         mem(mp,);
         mp[x][y]=;
         for(int i=;i<=;++i)
         {
             sc("%d%d",&x,&y);
             mp[x][y]=;
         }
         bfs(get(),);
         mem(mp,);
         for(int i=;i<=;++i)
         {
             sc("%d%d",&x,&y);
             mp[x][y]=;
         }
         bfs(get(),);
         if(ans)
             pr("YES\n");
         else
             pr("NO\n");
     }
     return ;
 }
 
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