Abdallah Yashir Blog

An OOP Approach to Solving the Famous Two Sum Algorithmic Problem

Abdallah Yashir Ramsing -

Problem Statement

Here's the description of the Two Sum problem:

Given an array of integers nums and an integer target, return indices of the two numbers such that they add up to target.

Example

Input: nums = [2,7,11,15], target = 9
Output: [0,1]
Explanation: Because nums[0] + nums[1] == 9, we return [0, 1].

My Solution

The trick part is here to return the indices. Therefore, you want a way to keep this data throughout the problem.

Thinking in terms of data structures, I use List as it's mutable. As a result, I don't need to keep track of which element we are currently looping.

I build the Class structure based on the final output I want.

Bonus: I also override the ToString method, which greatly helps to debug.

public class Solution {
    public int[] TwoSum(int[] nums, int target) {
        var item = new Item();
        var list = nums.ToList();
        item.firstValue = list.First();
        item.firstIndex = 0;
        list.RemoveAt(0);

        var counter = 0;
        while (list.Any())
        {
            
            var value = list.Where(x => item.firstValue + x == target);
            if (value.Any())
            {
                item.secondValue = value.FirstOrDefault();
                item.secondIndex = nums.ToList().LastIndexOf(item.secondValue);
                return item.ToResult();
            }
            else 
            {
                item.firstValue = list.FirstOrDefault();
                item.firstIndex = nums.ToList().IndexOf(item.firstValue);
                list.RemoveAt(0);
            }
        }

        return item.ToResult();
    }
}

public class Item
{
    public int firstValue;
    public int firstIndex;
    public int secondValue;
    public int secondIndex;

    public int[] ToResult()
    {
        return new int[] { this.firstIndex, this.secondIndex };
    }

    public override String ToString()
    {
        return $"First Value - First Index: {this.firstValue} - {this.firstIndex} --- Second Value - Second Index : {this.secondValue} - {this.secondIndex}";
    }
}

I usually use CodeWars to sharpen my programming skills but lately, I'm also been experimenting with LeetCode.

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