LEETCODE--Add Strings

最新推荐文章于 2020-05-15 14:33:20 发布

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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方法来实现两个以字符串形式给出的大数相加的问题。该方法适用于长度小于5100的非负整数字符串，确保了即使在处理极大数值时也能正确进行加法运算。

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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.

class Solution {
public:
    string addStrings(string num1, string num2) {
        int i = num1.length() - 1;
        int j = num2.length() - 1;
        string str;
        int carry = 0;
        while( i >= 0 || j >= 0 || carry){
            int sum = 0;
            if( i >= 0)
                sum += num1[i--] - '0';
            if( j >= 0)
                sum += num2[j--] - '0';
            sum += carry;
            carry = sum / 10;
            sum %= 10;
            str += to_string(sum); 
        }
        reverse(str.begin(), str.end());
        return str;
    }
};