Next Greater Element

Problem statement: Given an array, print the Next Greater Element (NGE) for every element. The Next greater Element for an element x is the first greater element on the right side of x in the array. Elements for which no greater element exist, consider the next greater element as -1.

Examples: For an array, the rightmost element always has the next greater element as -1. For an array that is sorted in decreasing order, all elements have the next greater element as -1. For the input array [4, 5, 2, 25], the next greater elements for each element are as follows.

Element       NGE
4      -->   5
5      -->   25
2      -->   25
25     -->   -1

For the input array [13, 7, 6, 12}, the next greater elements for each element are as follows.

Element        NGE
13      -->    -1
7       -->     12
6       -->     12
12      -->     -1