這是一份單向BFS一定會T的程式碼，挖坑等寫完雙向bfs再貼程式碼

  1 #include <bits/stdc++.h>
  2 #define _for(i,a,b) for(int i = (a);i < (b);i ++)
  3 using namespace std;
  4 struct cell
  5 {
  6     int t;
  7     int f;
  8 };
  9 
 10 typedef cell State[9];
 11 const int maxstate = 1000000;
 12 State st[maxstate],goal;
 
 13 int dist[maxstate];
 14 
 15 const int dx[] = {-1,1,0,0};
 16 const int dy[] = {0,0,1,-1};
 17 
 18 bool equ(State s)
 19 {
 20     _for(i,0,9)
 21         if(s[i].t != goal[i].t)    return false;
 22     return true;
 23 }
 24 
 25 bool limit(int x,int y)
 26 {
 27     return x>=0&&x<3
 
&&y>=0&&y<3;
 28 }
 29 
 30 set<int> vis;
 31 void init_lookup_table() {vis.clear();}
 32 bool try_to_insert(int s)
 33 {
 34     int v = 0;
 35     _for(i,0,9)    
 36     {
 37         if(st[s][i].t<0)
 38             v = v*10+9;
 39         else
 40             v = v*10
 
+(st[s][i].t*3)+st[s][i].f;
 41     }
 42     if(vis.count(v)) return false; 
 43     vis.insert(v);
 44     return true;
 45 }
 46 
 47 int bfs()
 48 {
 49     init_lookup_table();
 50     int front = 1,rear = 2;
 51     while(front<rear)
 52     {
 53         State& s = st[front];
 54         cout << dist[front] << endl;
 55         if(equ(s))    return front;
 56         int z;
 57         for(z = 0;z < 9;z ++) if(s[z].t<0) break;
 58         int x = z/3,y = z%3;
 59         _for(d,0,4)
 60         {
 61             int newx = x+dx[d];
 62             int newy = y+dy[d];
 63             int newz = newx*3+newy;
 64             if(limit(newx,newy))
 65             {
 66                 State& t = st[rear];
 67                 memcpy(&t,&s,sizeof(s));
 68                 if(newx==x)
 69                     t[z] = (cell){3-s[newz].t-s[newz].f,s[newz].f};
 70                 else if(newy==y)
 71                     t[z] = (cell){s[newz].f,s[newz].t};
 72                 t[newz] = (cell){-1,-1};
 73                 dist[rear] = dist[front]+1;
 74                 if(try_to_insert(rear)) rear ++;
 75             }
 76         }
 77         front ++;
 78     }
 79     return -1;
 80 }
 81 
 82 int main()
 83 {
 84     int tx,ty;
 85     while(scanf("%d%d",&tx,&ty)==2&&tx!=0)
 86     {
 87         _for(i,0,9) st[1][i] = (cell){0,1};
 88         st[1][(ty-1)*3+tx-1] = (cell){-1,-1};
 89         _for(i,0,9)
 90         {
 91             char c;
 92             cin >> c;
 93             if(c=='E')    goal[i].t = -1;
 94             else if(c=='W') goal[i].t = 0;
 95             else if(c=='R') goal[i].t = 1;
 96             else if(c=='B') goal[i].t = 2;
 97         }
 98         int ans = bfs();
 99         if(ans>0)    printf("%d\n",dist[ans]);
100         else printf("-1\n");
101         return 0;
102     }
103     return 0;
104 }