1426: [Blue Bridge Cup] [previous questions] JiuGongTu rearrangement

1426: [Blue Bridge Cup] [previous questions] JiuGongTu rearrangement

      Thinking : This question is the use of the BFS, the input as a string, with a map to re-sentence, then there is a problem is how to find whom you want to exchange, can take advantage of the structure, respectively existential state string (S), and now the number of steps required (sTEP), and on '' at what position (T), and then discuss go down, go up, go to the right, left, and where to go, cyclic take time out in four directions

  1 #include<bits/stdc++.h>
  2 using namespace std;
  3 const int N = 3010;
  4 map<string, int>m;
  5 string s1, s2;
  6 int ans = 0;
  7 struct node
  8 {
  9     string s;
 10     int step;
 11     int t;
 12 };
 13 void bfs()
 14 {
 15     queue<node>q;
 16     node e;
 17     e.s = s1;
 18     e.step = 0;
 19     for (int i = 0; i < 9; i++)
 20     {
 21         if (e.s[i] == '.')
 22         {
 23             e.t = i;
 24             break;
 25         }
 26     }
 27     q.push(e);
 28     while (!q.empty())
 29     {
 30         node w = q.front();
 31         q.pop();
 32         if (w.s == s2)
 33         {
 34             cout << w.step << endl;
 35             return;
 36         }
 37         int t = w.t;
 38         if (t + 3 < 9)//下
 39         {
 40             node e;
 41             e = w;
 42             swap(e.s[t], e.s[t + 3]);
 43             if (m[e.s] == 0)
 44             {
 45                 e.step = w.step + 1;
 46                 e.t = t + 3;
 47                 m[e.s]++;
 48                 q.push(e);
 49             }
 50         }
 51         if (t - 3 >= 0)//上
 52         {
 53             node e;
 54             e = w;
 55             swap(e.s[t], e.s[t - 3]);
 56             if (m[e.s] == 0)
 57             {
 58                 e.step = w.step + 1;
 59                 e.t = t-3;
 60                 m[e.s]++;
 61                 q.push(e);
 62             }
 63         }
 64         if (t==1||t==0||t==4||t==3||t==7||t==6)//右
 65         {
 66             node e;
 67             e = w;
 68             swap(e.s[t], e.s[t +1 ]);
 69             if (m[e.s] == 0)
 70             {
 71                 e.step = w.step + 1;
 72                 e.t = t + 1;
 73                 m[e.s]++;
 74                 q.push(e);
 75             }
 76         }
 77         if (t == 1 || t == 2 || t == 4 || t == 5 || t == 7 || t == 8)//左
 78         {
 79             node e;
 80             e = w;
 81             swap(e.s[t], e.s[t - 1]);
 82             if (m[e.s] == 0)
 83             {
 84                 e.t = t - 1;
 85                 m[e.s]++;
 86                 e.step = w.step + 1;
 87                 q.push(e);
 88             }
 89         }
 90     }
 91     if (q.empty())
 92     {
 93         cout << "-1" << endl;
 94     }
 95 }
 96 int main()
 97 {
 98     cin >> s1 >> s2;
 99     m[s1] = 1;
100     bfs();
101     return 0;
102 }