Question:

Given a string, find the first non-repeating character in it and return it’s index. If it doesn’t exist, return -1.

Example:

  1. s = "leetcode"
  2. return 0.
  4. s = "loveleetcode",
  5. return 2.

Solution:

  1. /**
  2.  * @param {string} s
  3.  * @return {number}
  4.  */
  5. var firstUniqChar = function(s) {
  6.   for (let i in s) {
  7.     if (s.indexOf(s[i]) === s.lastIndexOf(s[i])){
  8.       return i;
  9.     }
  10.   }
  11.   return -1;
  12. };

Runtime: 228 ms, faster than 6.39% of JavaScript online submissions for First Unique Character in a String.

  1. /**
  2.  * @param {string} s
  3.  * @return {number}
  4.  */
  5. var firstUniqChar = function(s) {
  6.   const obj = {}
  7.   for (let i in s) {
  8.     if(!obj[s[i]]) obj[s[i]] = 0;
  9.     obj[s[i]]++;
  10.   }
  11.   for (let j in s) {
  12.     if(obj[s[j]] === 1) {
  13.       return j;
  14.     }
  15.   }
  16.   return -1;
  17. };

Runtime: 252 ms, faster than 5.51% of JavaScript online submissions for First Unique Character in a String