【HDU】4985 Little Pony and Permutation 置换群

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传送门：【HDU】4985 Little Pony and Permutation

题目分析：基本置换群。内部排序反而错！

代码如下：

#include <cmath>#include <cstdio>#include <cstring>#include <algorithm>using namespace std ;#define REP( i , a , b ) for ( int i = ( a ) ; i <  ( b ) ; ++ i )#define FOR( i , a , b ) for ( int i = ( a ) ; i <= ( b ) ; ++ i )#define REV( i , a , b ) for ( int i = ( a ) ; i >= ( b ) ; -- i )#define CLR( a , x ) memset ( a , x , sizeof a )const int MAXN = 100005 ;int a[MAXN] ;bool vis[MAXN] ;int S[MAXN] , top ;int n ;void scanf ( int& x , char c = 0 ) {while ( ( c = getchar () ) < '0' || c > '9' ) ;x = c - '0' ;while ( ( c = getchar () ) >= '0' && c <= '9' ) x = x * 10 + c - '0' ;}void solve () {CLR ( vis , 0 ) ;FOR ( i , 1 , n ) scanf ( a[i] ) ;FOR ( i , 1 , n ) if ( !vis[i] ) {int now = i ;top = 0 ;while ( !vis[now] ) S[top ++] = now , vis[now] = 1 , now = a[now] ;printf ( "(" ) ;REP ( j , 0 , top - 1 ) printf ( "%d " , S[j] ) ;printf ( "%d)" , S[top - 1] ) ;}printf ( "\n" ) ;}int main () {while ( ~scanf ( "%d" , &n ) ) solve () ;return 0 ;}

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