clsk / digitadd

Problem description: Base 10 Math with Strings

Goal

Create a function(s) to implement the following signatures. The implementation must adhere to only string inputs and string outputs. In addition, all math operations must be no larger than one digit (Base10) + one digit (Base10). Thus the largest sum possible internally must be < 20.

Signatures

add(a, b) -> (sum) add(a, b, c, ...) -> sum

Expectations

Implement a testing strategy to verify your work.

Examples

add('1', '3') -> '4' add('2', '8') -> '10' add('12', '9') -> '21' add('19999', '22') -> '20021'

Extra Credit

How might you handle negative numbers? Consider ways you might implement this part of our Base 10 Math with Strings. This extra credit is primarily a thought exercise, no code need be implemented.

Solution

Approach

There are two ways to approach this.

 1345       1|3|4|5|                  1|3|4|5|
  832         8|3|2|           OR   +   8|3|2| 
  437         4|3|7|                  --------
-----       --------              R|E|S|U|L|T|
                                    +  |4|3|7|
                                      --------

Approaching the problem using the sum by row, then column appears easier from an algorithmic perspective. The reason being that, in that case carry-over, will every only be 1. Since the largest numbers (9+9) = 18. Store digit = 8, carry-over digit = 1. So, going to approach it that way to begin with.

Runing

The solution is written in JavaScript and should be running using NodeJS. To run all tests, install NodeJS in your OS of choice. Then, simply run using: node solution.js