1227. Repeated Substring Pattern

描述

Given a non-empty string check if it can be constructed by taking a substring of it and appending multiple copies of the substring together. You may assume the given string consists of lowercase English letters only and its length will not exceed 10000.

Example 1:

Input: "abab"

Output: True

Explanation: It's the substring "ab" twice.

Example 2:

Input: "aba"

Output: False

Example 3:

Input: "abcabcabcabc"

Output: True

Explanation: It's the substring "abc" four times. (And the substring "abcabc" twice.)

我起初用的是關聯容器，想直接算每個字母的出現次數，但很明顯這是錯誤的做法，它是要求連續子串。

參考博客：http://www.cnblogs.com/grandyang/p/6087347.html

所以採用遍歷的辦法，從長度爲1 長度爲一半的子字符串。

class Solution {
public:
    /**
     * @param s: a string
     * @return: return a boolean
     */
    bool repeatedSubstringPattern(string &s) {
        // write your code here
        int n=s.size();
        for(int i=n/2;i>0;--i){
            if(n%i==0){
                int c=n/i;
                string t="";
                for(int j=0;j<c;++j) t+=s.substr(0,i);
                if (t == s) return true;
            }
        }
        return false;
    }
};