UVA11549 计算机谜题（Floyd判圈算法）

 1 #include<iostream>
 2 #include<cstdio>
 3 #include<cstring>
 4 #include<cmath>
 5 #include<algorithm>
 6 #include<set>
 7 #include<sstream>
 8 using namespace std;
 9 /*int next1(int n,int k)
10 {
11     stringstream ss;
12     ss<<(long long)k*k;
13     string s=ss.str();
14     if(s.length()>n)s=s.substr(0,n);//结果太长，只取前n位
15     int ans;
16     stringstream ss2(s);
17     ss2>>ans;
18     return ans;
19 }*/
20 int buf[100];
21 int next2(int n,int k)
22 {
23     if(!k) return 0;
24     long long k2=(long long)k*k;
25     int L=0;
26     while(k2>0){
27         buf[L++]=k2%10;k2/=10;
28     }
29     if(n>L)n=L;
30     int ans=0;
31     for(int i=0;i<n;i++)
32     ans=ans*10+buf[--L];//把前min{n,L}位重新组合
33     return ans;
34 }
35 /*int main()
36 {
37     int T;
38     cin>>T;
39     while(T--)
40     {
41         int n,k;
42         cin>>n>>k;
43         set<int>s;
44         int ans=k;
45         while(!s.count(k))
46         {
47             s.insert(k);
48             if(k>ans)ans=k;
49             k=next1(n,k);
50         }
51         cout<<ans<<endl;
52     }
53     return 0;
54 }
55 */
56 int main()
57 {
58     int T;
59     cin>>T;
60     while(T--)
61     {
62         int n,k;
63         cin>>n>>k;
64         int ans=k;
65         int k1=k;int k2=k;
66         do{
67         k1=next2(n,k1);
68         k2=next2(n,k2);if(k2>ans)ans=k2;
69         k2=next2(n,k2);if(k2>ans)ans=k2;
70         }while(k1!=k2);
71         cout<<ans<<endl;
72     }
73     return 0;
74 }