459.Repeated Substring Pattern
===

###### tags: `Easy` `String`

[459. Repeated Substring Pattern](https://leetcode.com/problems/repeated-substring-pattern/)

### 題目描述

Given a string `s`, check if it can be constructed by taking a substring of it and appending multiple copies of the substring together.

### 範例

**Example 1:**

Input: s = "abab"
Output: true
Explanation: It is the substring "ab" twice.

**Example 2:**

Input: s = "aba"
Output: false

**Example 3:**

Input: s = "abcabcabcabc"
Output: true
Explanation: It is the substring "abc" four times or the substring "abcabc" twice.

**Constraints**:

* 1 <= `s.length` <= 10^4^
* `s` consists of lowercase English letters.

### 解答
#### Javascript

function repeatedSubstringPattern(s) {
  const len = s.length >> 1;
  let subString = '';

  for (let i = 0; i < len; i++) {
    subString += s[i];
    let tempString = subString;

    while (tempString.length < s.length) {
      tempString += subString;
    }

    if (tempString === s) return true;
  }

  return false;
}

function repeatedSubstringPattern2(s) {
  return s.repeat(2).slice(1, -1).includes(s);
}

> 下面一行的解是我弟教我的，跟鬼一樣。
> [name=Marsgoat][time=Aug 21, 2023]

### Reference

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