Next Greater Element Problem Statement

You are provided with an array or list ARR containing N positive integers. Your task is to determine the Next Greater Element (NGE) for each element in the array.

The Next Greater Element for an element X is the first element on the right side of X in the array ARR that is greater than X. If no such element exists, return -1.

Example:

Input:

ARR = [7, 12, 1, 20]

Output:

[12, 20, 20, -1]

Explanation:

The next greater element for 7 is 12, for 12 it is 20, for 1 it is 20, and for 20 there is no greater element to the right, so it is -1.

Constraints:

1

Question

Next Greater Element Problem Statement

You are provided with an array or list ARR containing N positive integers. Your task is to determine the Next Greater Element (NGE) for each element in the array.

The Next Greater Element for an element X is the first element on the right side of X in the array ARR that is greater than X. If no such element exists, return -1.

Example:

Input:

ARR = [7, 12, 1, 20]

Output:

[12, 20, 20, -1]

Explanation:

The next greater element for 7 is 12, for 12 it is 20, for 1 it is 20, and for 20 there is no greater element to the right, so it is -1.

Constraints:

1 <= T <= 100
1 <= N <= 5 * 10^3
1 <= ARR[i] <= 10^9
Time Limit: 1 sec

Note:

You are not required to print anything; it has already been taken care of. Just implement the function.

Accepted Answer

The task is to find the next greater element for each element in an array.

Iterate through the array from right to left
Use a stack to keep track of the elements
For each element, pop elements from the stack until a greater element is found or the stack is empty
If a greater element is found, it is the next greater element for the current element
If the stack becomes empty, there is no greater element to the right
Store the next greater element for each element in a result array