Circular Array Next Greater Element

Problem

For each element of a circular array, find the next strictly greater element.

Search up to n-1 positions ahead, wrapping around the end of the array. Iterate over the array twice (2n positions) with a monotonic stack of indices to resolve every element once.

Return a list where result[i] is the next greater value or -1 when none exists.

Hint

Loop twice over the indices; only push on the first pass to avoid duplicates.

Test cases

case 1

in: [[1,2,1]]

expected: [2,-1,2]

case 2

in: [[5,4,3,2,1]]

expected: [-1,5,5,5,5]

case 3

in: [[3,1,4,2]]

expected: [4,4,-1,3]

case 4

in: [[2,2,3]]

expected: [3,3,-1]

case 5

in: [[]]

expected: []

Starter codePython

def next_greater_circular(nums):
    # Your code here
    pass

5 test cases · run your code against them in the editor