std: bad_alloc runtime error in javascript code

Question

I was solving a problem in leetcode. The problem was find the length of longest substring. I solved the problem and the code is running perfectly on local machine and when I run the code on leetcode playground. But when I submit the code it shows runtime error with std:bad_alloc.

here is my code

const lengthOfLongestSubstring = (s) => {
  const allSubstring = [];
  let subIndex = 0;
  let count = 0;
  while (count < s.length) {
      allSubstring.push(s.substring(count, subIndex + 1));
      subIndex += 1;
      if (subIndex === s.length) {
          count += 1;
          subIndex = count;
      }
  }

  const valid = [];

  allSubstring.forEach((a) => {
      let validStr = '';
      a.split('').forEach((s, i) => {
          if (!validStr.includes(s)) {
              validStr += s;
          }
      });
      if (a.includes(validStr)) 
valid.push(validStr);
  });

  let longestSubString = '';
  valid.forEach((i) => {
      if (longestSubString.length < i.length) {
          longestSubString = i;
      }
  });

  return longestSubString.length;
}

I'm new at leetcode. I want to know what is wrong in this code?

Answer 1

This error occurs if you exceed Leetcode's allocated memory space for a submission. Your solution stores every one of the possible 2^n substrings, each of which has at most n characters: O(n * 2^n), which is quite high. You would want to come up with a more efficient solution to pass the test cases.

For learning purposes, here is a well-explained solution in O(n) space and time: https://leetcode.com/problems/longest-substring-without-repeating-characters/discuss/731639/JavaScript-Clean-Heavily-Commented-Solution.