415. Add Strings

Given two non-negative integers num1 and num2 represented as string, return the sum of num1 and num2.

Note:

  1. The length of both num1 and num2 is < 5100.
  2. Both num1 and num2 contains only digits 0-9.
  3. Both num1 and num2 does not contain any leading zero.
  4. You must not use any built-in BigInteger library or convert the inputs to integer directly.
 1 class Solution {
 2     public String addStrings(String num1, String num2) {
 3         StringBuilder sb = new StringBuilder();
 4         int carry = 0;
 5         int i = num1.length() - 1, j = num2.length() - 1;
 6         while (i >= 0 || j >= 0 || carry == 1){
 7             int x = i < 0 ? 0 : num1.charAt(i) - '0';
 8             int y = j < 0 ? 0 : num2.charAt(j) - '0';
 9             sb.append((x + y + carry) % 10);
10             carry = (x + y + carry) / 10;
11             i--;
12             j--;
13         }
14         return sb.reverse().toString();
15     }
16 }

 

posted @ 2020-02-07 06:38  北叶青藤  阅读(165)  评论(0)  编辑  收藏  举报