leetcode415---字符串大数相加
Given two non-negative numbers num1
and num2
represented as string, return the sum of num1
and num2
.
Note:
- The length of both
num1
andnum2
is < 5100. - Both
num1
andnum2
contains only digits0-9
. - Both
num1
andnum2
does not contain any leading zero. - You must not use any built-in BigInteger library or convert the inputs to integer directly.
我的第一个想法就是选好两个字符串,然后模拟加法进位,然后用一个字符串接着,同时记住进位,最后返回这个字符串的反转即可。
没有想到什么比较好的解决思路
public class Solution { public String addStrings(String num1, String num2) { StringBuilder sb = new StringBuilder(); int carry = 0; for(int i = num1.length() - 1, j = num2.length() - 1; i >= 0 || j >= 0; i--, j--){ int x = i < 0 ? 0 : num1.charAt(i) - '0'; int y = j < 0 ? 0 : num2.charAt(j) - '0'; sb.append((x + y + carry) % 10); carry = (x + y + carry) / 10; } if(carry != 0) sb.append(carry); return sb.reverse().toString(); } }