Question

Given an array of unsorted array and a number, determines all pair in array in array whose sum is equivalent to the given number

For example:

var arr = new[] { 1, 2, 5, 6, 7, 8, 9, 2, 10,3 };
var sum = 4;

from provided Array “arr” find all Pair who sum is 4

Answer:

Logic:

• Get the difference between array elements and given sum number
• Find the difference in reaming array to get the pairs

using System;

namespace FindSumPairInArray
{
    class Program
    {
        static void Main()
        {
            var arr = new[] { 1, 2, 5, 6, 7, 8, 9, 2, 10 };
            var sum = 4;

            PairSum(arr, sum);
            Console.ReadLine();
        }

        static void PairSum(int[] arr, int sum)
        {
            for (var i = 0; i < arr.Length; i++)
            {
                var rem = sum - arr[i];
                var ss = Array.IndexOf(arr, rem, i + 1);

                if (ss >= 0)
                    Console.WriteLine($"Sum array index {i} and {ss} values {arr[i]} + {arr[ss]} = {sum}");
            }
        }
    }
}