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poj 2406 Power Strings(KMP&思维)

时间:2014-07-06 00:33:22      阅读:253      评论:0      收藏:0      [点我收藏+]

标签:acm   c   算法   

Power Strings
Time Limit: 3000MS   Memory Limit: 65536K
Total Submissions: 31093   Accepted: 12974

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

Hint

This problem has huge input, use scanf instead of cin to avoid time limit exceed.

Source

题意

定义a^n为aaaaa...aaa。a为一个字符串。现在给你一个字符串问你把它写成a^n的形式。就你求出最大的n。

思路:

kmp水题。关键是思维。需要对KMP有一定认识。画个图就明白了。

bubuko.com,布布扣

用自己和自己匹配。一次失配后会形成上图的状态。剪头所指的位置都是相同的。因为自己和自己匹配嘛。所以只需要判断凸出去的长度能不能整除整个串的长度就行了。不行再往前移。行的话答案就是突出去的长度了。

详细见代码:

#include <iostream>
#include<stdio.h>
#include<string.h>
using namespace std;
const int maxn=1000100;
int f[maxn];
char txt[maxn];
void getf(char *p)
{
    int i,j,m=strlen(p);
    f[0]=f[1]=0;
    for(i=1;i<m;i++)
    {
        j=f[i];
        while(j&&p[i]!=p[j])
            j=f[j];
        f[i+1]=p[i]==p[j]?j+1:0;
    }
}
int main()
{
    int len,i,ans,t;

    while(~scanf("%s",txt))
    {
        if(txt[0]=='.')
            break;
        getf(txt);
        len=strlen(txt);
        i=len;
        ans=len-f[i];
        while(f[i])
        {
            t=len-f[i];
            if(len%t==0)
            {
                ans=len/t;
                break;
            }
            i=f[i];
        }
        printf("%d\n",ans);
    }
    return 0;
}


poj 2406 Power Strings(KMP&思维),布布扣,bubuko.com

poj 2406 Power Strings(KMP&思维)

标签:acm   c   算法   

原文地址:http://blog.csdn.net/bossup/article/details/37078203

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