clueless coding // TODO: be smarter

LeetCode 415. Add Strings: CPP Solution



Problem Statement

Given two non-negative integers num1 and num2 represented as string, return the sum of num1 and num2.

The value of each number is < 5100.

Num1 and num2 only contain 0-9 as digits.

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.

Function Signature (C++):
  string addStrings(string num1, string num2)

Inputs:
  num1 = "5"
  num2 = "193"

Outputs:
  "198"



TL;DR Code Solution

string addStrings(string num1, string num2) {

    string result;

    int indexOne = num1.length() - 1;
    int indexTwo = num2.length() - 1;
    int carry = 0;

    while (indexOne >= 0 || indexTwo >= 0 || carry) {
        int current = carry;

        if (indexOne >= 0) {
            current += num1[indexOne] - '0';
        }

        if (indexTwo >= 0) {
            current += num2[indexTwo] - '0';
        }

        carry = current / 10;
        current = current % 10;

        result = (char)(current + '0') + result;

        indexOne--;
        indexTwo--;
    }

    return result;

}