USACO 3.2 msquare 裸BFS

又是个裸BFS...

和西安网赛那道1006一样的，只不过加上了要记录方案。顺便复习map

记录方案直接在bfs队列的结点里加一个vector<int> opt，把从开头一直到当前结点的操作序列记下来

  1 /*
  2 PROB:msquare
  3 LANG:C++
  4 */
  5
  6 #include <iostream>
  7 #include <vector>
  8 #include <algorithm>
  9 #include <map>
 10 #include <queue>
 11 #include <cstdio>
 12 using namespace std;
 13
 14 struct node
 15 {
 16     vector<int> seq;
 17     int step;
 18     vector<int> opt;
 19     node(vector<int> x,int m,vector<int> o,int op):seq(x),step(m),opt(o)
 20     {
 21         opt.push_back(op);
 22     }
 23 };
 24
 25 map<vector<int>,int> M;
 26 queue<node> Q;
 27 vector<int> a;      //tmp2
 28 vector<int> A;      //init
 29 vector<int> y;      //tmp1
 30 vector<int> B;      //goal
 31 vector<int> ans;
 32 vector<int> yy;
 33 int b[10];
 34
 35 bool same()
 36 {
 37     for (int i=0;i<8;i++)
 38         if (y[i]!=b[i])
 39             return false;
 40     return true;
 41 }
 42
 43 int main()
 44 {
 45     freopen("msquare.in","r",stdin);
 46     freopen("msquare.out","w",stdout);
 47
 48     B.clear();
 49     a.clear();
 50     A.clear();
 51     for (int i=0;i<=3;i++)
 52     {
 53         cin>>b[i];
 54         A.push_back(i+1);
 55     }
 56     for (int i=7;i>=4;i--)
 57     {
 58         cin>>b[i];
 59         A.push_back(i+1);
 60     }
 61     for (int i=0;i<8;i++)
 62         B.push_back(b[i]);
 63
 64     //for (int i=0;i<8;i++)
 65     //    cout<<B[i]<<" "<<A[i]<<endl;
 66
 67     //A[0]=1;     A[1]=2;     A[2]=3;     A[3]=4;
 68     //A[4]=8;     A[5]=7;     A[6]=6;     A[7]=5;
 69     Q.push(node(A,0,a,0));
 70     M.insert(pair<vector<int>,int>(A,1));
 71     while (!Q.empty())
 72     {
 73         node tmp=Q.front();
 74         Q.pop();
 75         int st=tmp.step;
 76         //cout<<"step  "<<st<<endl;
 77         y=tmp.seq;
 78         yy=tmp.opt;
 79         if (same())
 80         {
 81             ans.clear();
 82             ans=tmp.opt;
 83             cout<<st<<endl;
 84             for (int i=1;i<=st;i++)
 85             {
 86                 char ch=ans[i]+‘A‘-1;
 87                 cout<<ch;
 88             }
 89             cout<<endl;
 90             break;
 91         }
 92         else
 93         {
 94             //opr1
 95             a=y;
 96             swap(a[0],a[4]);
 97             swap(a[1],a[5]);
 98             swap(a[2],a[6]);
 99             swap(a[3],a[7]);
100             if (!M.count(a))
101             {
102                 M.insert(pair<vector<int>,int>(a,1));
103                 Q.push(node(a,st+1,yy,1));
104             }
105             //opr2
106             a=y;
107             int t1=a[3],t2=a[7];
108             a[3]=a[2];  a[7]=a[6];
109             a[2]=a[1];  a[6]=a[5];
110             a[1]=a[0];  a[5]=a[4];
111             a[0]=t1;    a[4]=t2;
112             if (!M.count(a))
113             {
114                 M.insert(pair<vector<int>,int>(a,1));
115                 Q.push(node(a,st+1,yy,2));
116             }
117             //opr3
118             a=y;
119             int tm=a[1];
120             a[1]=a[5];  a[5]=a[6];  a[6]=a[2];  a[2]=tm;
121             if (!M.count(a))
122             {
123                 M.insert(pair<vector<int>,int>(a,1));
124                 Q.push(node(a,st+1,yy,3));
125             }
126         }
127     }
128
129     return 0;
130 }