poj 1077 八数码

  1 #include<iostream>
  2 #include<queue>
  3 #include<algorithm>
  4 #include<string>
  5 #include<cstring>
  6 #include<cstdio>
  7 //正向广度搜索
  8 //把“x"当初0
  9 using namespace std;
 10 
 11 const int maxn = 1000000;
 12 
 13 int fac[] = { 1, 1, 2, 6, 24, 120, 720, 5040, 40320, 362880 };   //康拖展开判重
 14 //         0!1!2!3! 4! 5!  6!  7!   8!    9!
 15 int vis[maxn];
 16 
 17 int get_priority(int s[]){        //康拖展开求该序列的hash值
 18     int sum = 0;
 19     for (int i = 0; i<9; i++){
 20         int cnt = 0;
 21         for (int j = i + 1; j<9; j++)
 22             if (s[i]>s[j])
 23                 cnt++;
 24         sum += (cnt*fac[9 - i - 1]);
 25     }
 26     return sum + 1;
 27 }
 28 
 29 struct node{
 30     int s[9];
 31     int loc;    //“0”的位置,把“x"当0
 32     int status;     //康拖展开的hash值
 33     string path;    //路径
 34 }start;
 35 
 36 string path;
 37 int aim = 46234;  //123456780对应的康拖展开的hash值
 38 int dir[4][2] = { { -1, 0 }, { 1, 0 }, { 0, -1 }, { 0, 1 } };//u,d,l,r
 39 char indexs[5] = "udlr";//正向搜索
 40 
 41 int BFS(){
 42     queue<node> q;
 43     while (!q.empty())
 44         q.pop();
 45     node cur, next;
 46     q.push(start);
 47     int x, y;
 48     while (!q.empty()){
 49         cur = q.front();
 50         q.pop();
 51         if (cur.status == aim){
 52             path = cur.path;
 53             return 1;
 54         }
 55         x = cur.loc / 3;
 56         y = cur.loc % 3;
 57         for (int i = 0; i<4; i++){
 58             int tx = x + dir[i][0];
 59             int ty = y + dir[i][1];
 60             if (tx<0 || tx >= 3 || ty<0 || ty >= 3)
 61                 continue;
 62             next = cur;
 63             next.loc = tx * 3 + ty;
 64             next.s[cur.loc] = next.s[next.loc];
 65             next.s[next.loc] = 0;
 66             next.status = get_priority(next.s);
 67             if (!vis[next.status]){
 68                 vis[next.status] = 1;
 69                 next.path = next.path + indexs[i];
 70                 if (next.status == aim){
 71                     path = next.path;
 72                     return 1;
 73                 }
 74                 q.push(next);
 75             }
 76         }
 77     }
 78     return 0;
 79 }
 80 
 81 int main(){
 82 
 83     //freopen("input.txt","r",stdin);
 84 
 85     char ch;
 86     while (cin >> ch){
 87         if (ch == ‘x‘){
 88             start.s[0] = 0;
 89             start.loc = 0;
 90         }
 91         else
 92             start.s[0] = ch - ‘0‘;
 93         for (int i = 1; i<9; i++){
 94             cin >> ch;
 95             if (ch == ‘x‘){
 96                 start.s[i] = 0;
 97                 start.loc = i;
 98             }
 99             else
100                 start.s[i] = ch - ‘0‘;
101         }
102         start.status = get_priority(start.s);
103         memset(vis, 0, sizeof(vis));
104         if (BFS())
105             cout << path << endl;
106         else
107             printf("unsolvable\n");
108     }
109     return 0;
110 }