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 ;

 }

 /**************************************************************************************/