/*
 * @lc app=leetcode.cn id=415 lang=javascript
 *
 * [415] 字符串相加
 */

// @lc code=start
/**
 * @param {string} num1
 * @param {string} num2
 * @return {string}
 */
var addStrings = function (num1, num2) {
  let i = num1.length - 1;
  let j = num2.length - 1;
  let carry = 0;
  let result = '';

  while (i >= 0 || j >= 0 || carry > 0) {
    const x = i >= 0 ? +num1[i] : 0;
    const y = j >= 0 ? +num2[j] : 0;
    const cur = x + y + carry
    result = cur % 10 + result
    carry = Math.floor(cur / 10)
    i--;
    j--;
  }
  return result;
};
// @lc code=end

console.log(addStrings('1', '9'))
console.log(addStrings('11', '123'))