averagePair.js

// Write a function called averagePair. Given a sorted array of integers 
// and a target average, determine if there is a pair of values in the 
// array where the average of the pair equals the target average. There 
// may be more than one pair that matches the average target.

// Bonus Constraints:

// Time: O(N)

// Space: O(1)

// Sample Input:

// averagePair([1,2,3],2.5) // true
// averagePair([1,3,3,5,6,7,10,12,19],8) // true
// averagePair([-1,0,3,4,5,6], 4.1) // false
// averagePair([],4) // false


function averagePair(arr, ave){
    let sum = ave * 2;
    if(arr.length === 0){
        return false;
    }
    arr.sort((a,b) =>a-b);
    let left = 0;
    let right = arr.length - 1;
    while(left < right){
        if(arr[left] + arr[right] < sum){
            left++;
        }
        else if(arr[left] + arr[right] > sum){
            right--;
        }
        else{
            return true;
        }
    }
    return false;
}

console.log(averagePair([],4))