415. Add Strings

字符串形式加法

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本文介绍了一个LeetCode上的题目，该题目要求实现两个大数的加法运算，输入为两个非负整数的字符串形式，输出也为字符串形式。文章提供了一个C++解决方案，通过将较短的字符串前面补零来统一长度，然后从最低位开始逐位相加。

题目来源【Leetcode】

You are given a string representing an attendance record for a student. The record only contains the following three characters:

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.

这道题就是求两个数的和，只不过是以字符串的形式进行，代码如下：

class Solution {
public:
    string addStrings(string num1, string num2) {
        string s = "";
        int temp = 0;
        int l1 = num1.size();
        int l2 = num2.size();
        if(l1 < l2){
            for(int i = 0; i < l2-l1; i++)
                num1 = "0" + num1;
        }
        else {
             for(int i = 0; i < l1-l2; i++)
                num2 = "0" + num2;
        }
        for(int i = num1.length()-1; i >= 0; i--){
            int t = num1[i]+num2[i]+temp-48*2;
            if(t > 9) {
                temp = 1;
                t = t-10;
            }
            else temp = 0;
            s = char(t+48) + s;
        }
        if(temp == 1) s = "1" + s;
        return s;
    }
};