Substring with Concatenation of All Words

Description

You are given a string, s, and a list of words, words, that are all of the same length. Find all starting indices of substring(s) in s that is a concatenation of each word in words exactly once and without any intervening characters.

 

Example 1:

Input:
  s = "barfoothefoobarman",
  words = ["foo","bar"]
Output: [0,9]
Explanation: Substrings starting at index 0 and 9 are "barfoo" and "foobar" respectively.
The output order does not matter, returning [9,0] is fine too.

Example 2:

Input:
  s = "wordgoodgoodgoodbestword",
  words = ["word","good","best","word"]
Output: []

Solution(javascript)

/**
 * @param {string} s
 * @param {string[]} words
 * @return {number[]}
 */
var findSubstring = function(s, words) {
    if(!words.length) return [];
    
    const wordLen = words[0].length;
    const arrLen = words.reduce((acc,element) => acc + element.length, 0);
    const re = new RegExp('(.{' + wordLen + '})');
    words = words.sort();
    
    function equalArr(arr1, arr2) {
        for(let j = 0; j < arr1.length; j++){
            if(arr1[j] != arr2[j]) return false;
        }
        return true;
    }
    
    let rst = [];
    for(let i = 0; i <= s.length - arrLen; i++) {
        const splitArr = s.slice(i, i+arrLen).split(re).filter(O=>O).sort();
        if(equalArr(words, splitArr)) rst.push(i);
    }
    
    return rst;
};