Question:

Given a string S, return the “reversed” string where all characters that are not a letter stay in the same place, and all letters reverse their positions.

Example:

  1. Input: "ab-cd"
  2. Output: "dc-ba"
  1. Input: "a-bC-dEf-ghIj"
  2. Output: "j-Ih-gfE-dCba"

Solution:

  1. /**
  2.  * @param {string} S
  3.  * @return {string}
  4.  */
  5. var reverseOnlyLetters = function(S) {
  6.   const arr = S.split('');
  7.   const len = arr.length;
  8.   const regx = /[A-Za-z]+/;
  9.   let left = 0;
  10.   let right = len-1;
  11.   let temp;
  12.   while (left <= right) {
  13.     if (!regx.test(arr[left])) {
  14.       left ++;
  15.       continue;
  16.     }
  18.     if (!regx.test(arr[right])) {
  19.       right --;
  20.       continue;
  21.     }
  22.     temp = arr[left];
  23.     arr[left] = arr[right];
  24.     arr[right] = temp;
  25.     left ++;
  26.     right --;
  27.   }
  28.   return arr.join('');
  29. };

Runtime: 72 ms, faster than 14.75% of JavaScript online submissions for Reverse Only Letters.