Leetcode0371-Sum of Two Integers.js

/**
 * https://leetcode.com/problems/sum-of-two-integers/description/
 * Difficulty:Medium
 *
Calculate the sum of two integers a and b, but you are not allowed to use the operator + and -.

Example 1:

Input: a = 1, b = 2
Output: 3
Example 2:

Input: a = -2, b = 3
Output: 1

 //https://developer.mozilla.org/zh-TW/docs/Web/JavaScript/Reference/Operators/Bitwise_Operators
/**
 * @param {number} a
 * @param {number} b
 * @return {number}
 */
var getSum = function(a, b) {
  
  const sum = a ^ b; // XOR derives the sum bits, without carry
  const carry = (a & b) << 1; // AND derives the carry bits
  
  if (!carry) {
    return sum;
  }
  
  return getSum(sum, carry);
}
  
  
  
function getSum2(a, b) {
  var s1, s2;
  s1 = parseNumberToStringWithPN(num1);
  s2 = parseNumberToStringWithPN(num2);

  // Change number to the string whose length is same as the value. 'p' means positive and 'n' means negative.
  // EX. 2 => pp
  // EX. -4 => nnnn
  function parseNumberToStringWithPN(num) {
    if(num >= 0) {
      return 'p'.repeat(num);
    } else {
      return 'n'.repeat(num*-1);
    }
  }

  // If one number is positive and another is negative, using substr() to both strings until anyone's length to be 0
  if((num1 < 0 || num2 < 0) && !(num1 < 0 && num2 < 0)) {
    do {
      s1 = s1.substr(1);
      s2 = s2.substr(1);
    } while(s1.length > 0 && s2.length > 0);
  }
  
  // Use concat() for adding two variables
  var result = s1.concat(s2);
  
  if(result.indexOf('n') > -1) { 
    
    // Negative result
    return result.length * -1;
  } else { 
    
    // Positive result
    return result.length;
  }
}