# power string kmp算法

Power Strings

 Time Limit: 3000MS Memory Limit: 65536KB 64bit IO Format: %I64d & %I64u

Description

Given two strings a and b we define a*b to be their concatenation. For example, if a = “abc” and b = “def” then a*b = “abcdef”. If we think of concatenation as multiplication, exponentiation by a non-negative integer is defined in the normal way: a^0 = “” (the empty string) and a^(n+1) = a*(a^n).

Input

Each test case is a line of input representing s, a string of printable characters. The length of s will be at least 1 and will not exceed 1 million characters. A line containing a period follows the last test case.

Output

For each s you should print the largest n such that s = a^n for some string a.

Sample Input

```abcd
aaaa
ababab
.
```

Sample Output

```1
4
```

3

``````#include <iostream>
#include <algorithm>
#include <cstdio>
#include <cstring>
#define maxn 1000005
using namespace std;
char str[maxn];
int next[maxn],len;
void get_next();
int main()
{
while(~scanf("%s",str)&&strcmp(str,"."))
{
len=strlen(str);
get_next();
int ans=1;
if(len%(len-next[len])==0)
ans=len/(len-next[len]);
printf("%d\n",ans);
}
}
void get_next()
{
int i=0,j=-1;
next[0]=-1;
while(i<len)
{
if(j==-1||str[i]==str[j])
{
i++;
j++;
if(str[i]!=str[j])//仅仅满足j==-1
next[i]=j;
else
next[i]=next[j];//仅仅满足str[i]==str[j]
}
else
j=next[j];
}
}
``````

原文作者：KMP算法
原文地址: https://blog.csdn.net/a716121/article/details/47906373
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