KMP + 求最小循環節 --- POJ 2406 Power Strings

 Power Strings

Problem's Link:  http://poj.org/problem?id=2406

---

 

Mean: 

給你一個字符串，讓你求這個字符串最多可以被表示成最小循環節重複多少次獲得。

analyse:

KMP之next數組的運用。裸的求最小循環節。

Time complexity: O(N)

 

Source code: 

/*
* this code is made by crazyacking
* Verdict: Accepted
* Submission Date: 2015-07-28-08.23
* Time: 0MS
* Memory: 137KB
*/
#include <queue>
#include <cstdio>
#include <set>
#include <string>
#include <stack>
#include <cmath>
#include <climits>
#include <map>
#include <cstdlib>
#include <iostream>
#include <vector>
#include <algorithm>
#include <cstring>
#define  LL long long
#define  ULL unsigned long long
using namespace std;
const int MAXN = 1000010;
char s [ MAXN ];
int Next [ MAXN ];
void getNext( int len)
{
      Next [ 0 ] = 0;
      for( int i = 1 , k = 0; i < len; ++ i)
      {
            while(s [ i ] !=s [ k ] && k) k = Next [ k - 1 ];
            if(s [ i ] ==s [ k ]) ++ k;
            Next [ i ] = k;
      }
}
int main()
{
      ios_base :: sync_with_stdio( false);
      cin . tie( 0);
      while( ~ scanf( "%s" ,s) && s [ 0 ] != '.')
      {
            int len = strlen(s);
            getNext( len);
            int min_cycle = len - Next [ len - 1 ];
            if( len % min_cycle != 0) printf( "1 \n ");
            else printf( "%d \n " , len / min_cycle);
      }
      return 0;
}
/*

*/