Challenge: Next Greater Element Using a Stack

Statement

Implement a NextGreaterElement() function that takes an array of integers, arr, as input and returns the next greater number for every element in the array.

The next greater number for a number arr[i] is the first number to its right that is greater than arr[i]. If no such number exists, return -1 for this number.

Constraints:

• $1 \leq$ arr.length $\leq 10^{3}$
• $0 \leq$ arr[i] $\leq 10^{3}$

Examples