# 415.AddStrings

// https://leetcode-cn.com/problems/add-strings/

/**
 * @param {string} num1
 * @param {string} num2
 * @return {string}
 */
var addStrings = function(num1, num2) {
  let [i, j] = [num1.length-1, num2.length-1];
  let ans = '';
  let add = 0;
  for ( ; i >= 0 || j >= 0; i--, j--) {
    let a = i >= 0 ? +num1[i] : 0;
    let b = j >= 0 ? +num2[j] : 0;
    let sum = a + b + add;
    ans = sum % 10 + ans;
    add = Math.floor(sum / 10);
  }

  add && (ans = add + ans);
  return ans;
};