LeetCode——Add Strings

Question

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.

解题思路

这道题就是所谓的大整数加法操作，因为超过了计算机所能表示的范围数，所以用字符串表示，然后注意到就是，当两个长度不一样的时候，可以考虑往一个较短的字符串补‘0’，让两个字符串的长度保持一致。

具体实现

class Solution {public:    // 大整数加法    string addStrings(string num1, string num2) {        string n1(num1.rbegin(), num1.rend());        string n2(num2.rbegin(), num2.rend());        int size1 = n1.length();        int size2 = n2.length();        if (size1 < size2) {            for (int i = 0; i < size2 - size1; i++) {                n1 += '0';            }        }        if (size1 > size2) {            for (int j = 0; j < size1 - size2; j++) {                n2 += '0';            }        }        int remainer = 0;        string str;        for (int i = 0; i < n1.length(); i++) {            int sum = n1[i] - 48 + n2[i] - 48 + remainer;            remainer = 0;            if (sum >= 10) {                sum = sum - 10;                remainer = 1;            }            char tmp = sum + 48;            str += tmp;        }        if (remainer == 1)            str += '1';        string str1(str.rbegin(), str.rend());        return str1;    }};