[LeetCode] 415.Add Strings

[LeetCode] 415.Add Strings

• 题目描述
• 解题思路
• 实验代码

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题目描述

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.

解题思路

这道题其实也不复杂，我用了reverse()函数解决，主要是想清楚进位，合位直接的关系，以及注意好ASCII码与字符的关系以及转换，这道题就能得到解决。

实验代码

class Solution {
public:
    string addStrings(string num1, string num2) {
        string sum;
        if (num1.size() > num2.size())
            return addStrings(num2, num1);
        reverse(num1.begin(), num1.end());
        reverse(num2.begin(), num2.end());
        int ca = 0, i = 0;
        for (i; i < num1.size(); i++) {
            int cd = (num1[i]-'0'+num2[i]-'0'+ca)%10;
            ca = (num1[i]-'0'+num2[i]-'0'+ca)/10;
            sum += to_string(cd);
        }
        for (i; i < num2.size(); i++) {
            int cd = (num2[i]-'0'+ca)%10;
            ca = (num2[i]-'0'+ca)/10;
            sum += to_string(cd);
        }
        if (ca == 1)
            sum += "1";
        reverse(sum.begin(), sum.end());
        return sum;
    }
};