Find a pair of elements from an array whose sum equals a given number in javascript

 

Find a pair of elements from an array whose sum equals a given number in javascript:

We can find a pair of elements from an array whose sum equals a given number in javascript in a different way. Listing the easiest methods.

Solution 1 :

1. The first thing is  to sort an array
2. Store the first element of an array
3. Store the last element of an array
4. Add the first and last element as theSum
5. If tempSum === theSum then add the pair as an element to an object

function pairMatchingSum (arr, sum)
{
    var start, end, tempSum;
    var i = 0 ;
    var j = arr.length - 1;
    // Create a new Object instance
    var pairValues = {};
    var sortedArray = arr.sort();
    while (i !== j)
    {
        start = sortedArray[i];
        end = sortedArray[j];
        tempSum = start + end;
        if (tempSum === sum)
        {
            // Add matching pair to the Object. Object does not allow duplicate keys.
            pairValues[start +'-'+ end] = true;
            i++;
            j--;
        }
        else if (tempSum > sum)
        {
            j--;
        }
        else
        {   
            i++;
        }
    }
    console.info("Pairs of values", Object.keys(pairValues));
}

var array = [2, 3, 2, 5, 4, 5, 5, 5, 5, 9, 6, 8, 8, 7];
var sum = 10;
pairMatchingSum(array, sum);

Solution 2 :

Using the for-loop with HashMap function

let pairMatchingSum = (array, sum) => 
{
    let mapObject = {},
    mathcingPair = []

    for (let i = 0; i < array.length; i++)
    {
        if (mapObject[array[i]])
        {
            mathcingPair.push([mapObject[array[i]], array[i]])
        }
        else
        {
            mapObject[sum - array[i]] = array[i];
        }
    }
    return mathcingPair;
}

console.log(pairMatchingSum([10,20,10,40,50,60,70,30],50));

 

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