LeetCode #415 - Add Strings

最新推荐文章于 2020-08-04 22:32:35 发布

原创最新推荐文章于 2020-08-04 22:32:35 发布 · 202 阅读

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本文介绍了一种不使用内置大数库或直接转换为整数的两个非负整数字符串相加的方法。通过模拟传统的竖式加法过程，逐位进行加法运算并处理进位，实现了对超长数字字符串的有效求和。

题目描述：

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.

将两个数字字符串相加，方法就是模拟竖式相加。

class Solution {
public:
    string addStrings(string num1, string num2) {
        int i=num1.size()-1;
        int j=num2.size()-1;
        int sum=0;
        int carry=0;
        string result;
        while(i>=0&&j>=0)
        {
            sum=carry+num1[i]-'0'+num2[j]-'0';
            result=to_string(sum%10)+result;
            carry=sum/10;
            i--;
            j--;
        }
        while(i>=0)
        {
            sum=carry+num1[i]-'0';
            result=to_string(sum%10)+result;
            carry=sum/10;
            i--;
        }
        while(j>=0)
        {
            sum=carry+num2[j]-'0';
            result=to_string(sum%10)+result;
            carry=sum/10;
            j--;
        }
        if(carry==1) result="1"+result;
        return result;
    }
};