题目
Given two non-negative integers num1 and num2 represented as string, return the sum of num1 and num2.
Note:
- The length of both num1 and num2 is < 5100.
- Both num1 and num2 contains only digits 0-9.
- Both num1 and num2 does not contain any leading zero.
- You must not use any built-in BigInteger library or convert the inputs to integer directly.
难度
Easy
方法
从低位到高位相加，每一位的结果为除10取余，如果有进位1，则在下一位求和的时候需要+1，循环处理即可。注意最高位相加后如果有进位，需要在结果的最前面补1
python代码
class Solution(object):
def addStrings(self, num1, num2):
"""
:type num1: str
:type num2: str
:rtype: str
"""
i = len(num1) - 1
j = len(num2) - 1
num = ""
carry = 0
while i >= 0 or j >= 0:
result = carry
if i >= 0:
result += int(num1[i])
if j >= 0:
result += int(num2[j])
if result >= 10:
carry = 1
else:
carry = 0
num = str(result % 10) + num
i -= 1
j -= 1
if carry == 1:
num = "1" + num
return num
assert Solution().addStrings("111", "234965") == "235076"
assert Solution().addStrings("999", "1") == "1000"
