[字符串运算]字符串相加

class Solution:
    def addStrings(self, num1: str, num2: str) -> str:

        n = len(num1)
        m = len(num2)

        if n>m:
            for _ in range(n-m):
                num2 = '0'+num2
        
        if n<m:
            for _ in range(m-n):
                num1 = '0'+num1

        res = [0]*(len(num1)+1)
        temp = 0

        for i in range(len(num1)-1,-1,-1):
            t = (ord(num1[i])-ord('0')) + (ord(num2[i])-ord('0')) + temp
            if t>=10:
                res[i+1] = t-10
                temp = 1
            else:
                res[i+1] = t
                temp = 0
        
        if temp == 1:
            res[0] = temp
        
        if res[0] == 0:
            return ("".join(map(str,res[1:])))
        else:
            return ("".join(map(str,res)))