leaders-in-an-array.md

Leaders in an array

Problem Description

Given an integer array A containing N distinct integers, you have to find all the leaders in array A. An element is a leader if it is strictly greater than all the elements to its right side.

NOTE: The rightmost element is always a leader.

Problem Constraints

1 <= N <= 10^5
1 <= A[i] <= 10^8

Input Format

There is a single input argument which a integer array A

Output Format

Return an integer array denoting all the leader elements of the array.

Example Input

Input 1:
A = [16, 17, 4, 3, 5, 2]

Input 2:
A = [5, 4]

Example Output

Output 1:
[17, 2, 5]

Output 2:
[5, 4]

Example Explanation

Explanation 1:
Element 17 is strictly greater than all the elements on the right side to it.
Element 2 is strictly greater than all the elements on the right side to it.
Element 5 is strictly greater than all the elements on the right side to it.
So we will return these three elements i.e [17, 2, 5], we can also return [2, 5, 17] or [5, 2, 17] or any other ordering.

Explanation 2:
Element 5 is strictly greater than all the elements on the right side to it.
Element 4 is strictly greater than all the elements on the right side to it.
So we will return these two elements i.e [5, 4], we can also any other ordering.

Output

function findLeaders(A) {
    let leaders = [];
    if (A.length === 0) return leaders;

    let maxFromRight = A[A.length - 1];
    leaders.push(maxFromRight);

    for (let i = A.length - 2; i >= 0; i--) {
        if (A[i] > maxFromRight) {
            maxFromRight = A[i];
            leaders.push(maxFromRight);
        }
    }

    return leaders.reverse(); // Reversing to get the original order
}