A*

 

https://www.luogu.org/problemnew/show/P1379

  1 #include <cstdio>
  2 #include <cstdlib>
  3 #include <cstring>
  4 #include <cmath>
  5 #include <map>
  6 #include <queue>
  7 #include <algorithm>
  8 using namespace std;
  9 #define ll long long
 10 const int maxn=1e6+10;
 11 const int ci=1e6;
 12 
 13 struct node
 14 {
 15     int a[9],pos;
 16 };
 17 
 18 struct rec
 19 {
 20     ///g:from source to this condition(actual)
 21     ///h:from this condition to destination(predict)
 22     node d;
 23     int g,tot;
 24     bool operator<(const rec &b) const
 25     {
 26         ///绝对不能仅仅是b.tot<tot
 27         if (b.tot==tot)
 28             return b.g<g;
 29         return b.tot<tot;
 30     }
 31 };
 32 priority_queue<rec> st;
 33 
 34 int f[][5]={
 35 {2,1,3},
 36 {3,0,2,4},
 37 {2,1,5},
 38 {3,0,4,6},
 39 {4,1,3,5,7},
 40 {3,2,4,8},
 41 {2,3,7},
 42 {3,4,6,8},
 43 {2,5,7},
 44 };
 45 
 46 int dest[]={1,2,3,8,0,4,7,6,5};
 47 
 48 map<ll,int> m;
 49 
 50 ll cal(int a[])
 51 {
 52     int i;
 53     ll j=1,sum=0;
 54     for (i=0;i<9;i++)
 55     {
 56         sum+=j*a[i];
 57         j*=9;
 58     }
 59     return sum;
 60 }
 61 
 62 int predict(int a[])
 63 {
 64     int sum=0,i;
 65     for (i=0;i<9;i++)
 66         sum+=a[i]!=dest[i];
 67     if (sum==0)
 68         sum=1;
 69     return sum-1;
 70 }
 71 
 72 void pr(int a[])
 73 {
 74     int i;
 75     for (i=0;i<9;i++)
 76     {
 77         printf("%d ",a[i]);
 78         if (i%3==2)
 79             printf("\n");
 80     }
 81     printf("\n");
 82 }
 83 
 84 int main()
 85 {
 86     char s[10];
 87     int i,g,pos;
 88     ll sum,sumdest;
 89     node d;
 90 
 91     scanf("%s",s);
 92     for (i=0;i<9;i++)
 93     {
 94         d.a[i]=s[i]-48;
 95         if (d.a[i]==0)
 96             d.pos=i;
 97     }
 98     sum=cal(d.a);
 99     m[sum]=0;
100     sumdest=cal(dest);
101     if (sum==sumdest)
102     {
103         printf("0");
104         return 0;
105     }
106 
107     st.push({d,0,predict(d.a)});
108     while (!st.empty())
109     {
110         d=st.top().d;
111 //            pr(d.a);///
112         g=st.top().g;
113         st.pop();
114         pos=d.pos;
115         for (i=1;i<=f[pos][0];i++)
116         {
117             swap(d.a[pos],d.a[f[pos][i]]);
118             sum=cal(d.a);
119             if (sum==sumdest)
120             {
121                 printf("%d",g+1);
122                 return 0;
123             }
124             ///遇到比之前好的，则修改！
125             if (m.find(sum)==m.end() || m[sum]<g+1)
126             {
127                 m[sum]=g+1;
128                 d.pos=f[pos][i];
129                 st.push({d,g+1,g+1+predict(d.a)});
130             }
131             swap(d.a[pos],d.a[f[pos][i]]);
132         }
133     }
134     return 0;
135 }
136 /*
137 123804765
138 
139 023184765
140 
141 021345678
142 
143 201534786
144 
145 201534786
146 19
147 */

 

posted @ 2018-12-05 15:49  congmingyige  阅读(332)  评论(0)  编辑  收藏  举报