Next Greater Element II Visualization & Animation

Finds next greater elements in a circular array by iterating twice with modulo and a monotonic stack; O(n).

## What is it? Same as Next Greater Element I but the array is treated as **circular** — after the last element, wrap around to the beginning. Find the next greater element for each position in this circular array. ## How it works - Iterate twice through the array (indices 0 to 2n-1) using modulo to simulate circularity - Use a monotonic decreasing stack of indices - On the first pass, build the stack normally - On the second pass, pop elements from the stack whose next greater is found in the "wrap-around" portion - Elements still in the stack after both passes have no greater element → -1 ## When to use - Circular arrays where the search wraps around - Extension practice for the basic Next Greater Element problem ## Key Points - The double-pass trick `(i % n)` simulates circularity without duplicating the array - O(n) time, O(n) space - Only need at most 2n iterations because after a full extra loop no new greater elements can be found

Category: algorithms

Difficulty: intermediate

Time Complexity: O(n)

Space Complexity: O(n)

Next Greater Element II

intermediate

Finds next greater elements in a circular array by iterating twice with modulo and a monotonic stack; O(n).

GFGLeetCode
Init
PASS 1
empty
Monotonic Stack
i
1
[0]
2
[1]
3
[2]
4
[3]
3
[4]
NGE Result
?
[0]
?
[1]
?
[2]
?
[3]
?
[4]
Initialize: empty stack, all NGE = ? Two passes over the circular array.