poj 2369 Permutations

这是一道简单的置换群的问题；

#include<iostream>
 #include<cstdio>
 #include<cstdlib>
 #include<algorithm>
 #include<cmath>
 #include<queue>
 #include<set>
 #include<map>
 #include<cstring>
 #include<vector>
 #include<string>
 #define LL long long
 using namespace std;
 int Gcd( int a , int b )
 {
     return b == 0? a : Gcd( b , a % b );    
 }
 int Solve( int N , int num[] )
 {
    int ans = 1;
    bool visit[1024] = { 0 };
    for( int i = 1; i <= N; i ++ )
    {
         if( !visit[i] )
         {
             visit[i] = true;
             int t = num[i],cnt=1;
             while( i != t )
             {
                   visit[t] = true;
                   cnt ++;
                   t = num[t];
             }
             ans = (ans/Gcd( ans , cnt ))*cnt;
         }        
    }
    return ans;    
 }
 int main(  )
 {
     int num[1024],N;
     while( scanf( "%d",&N )==1 )
     {
          for( int i = 1 ; i <= N ; i ++ )
          {
               scanf( "%d",&num[i] );        
          }    
          printf( "%d\n",Solve( N ,num ) );
     }
     //system( "pause" );
     return 0;
 }