Next Variants

These problems focus on monotonic stack applications, circularity, and range queries.

LeetCode 496 ➔ Next Greater Element I: The basic introduction using a HashMap and a Monotonic Stack.
LeetCode 503 ➔ Next Greater Element II: Introduces Circular Arrays. Requires the "double iteration" or "modulo" technique.
LeetCode 556 ➔ Next Greater Element III: A direct bridge to the Next Permutation algorithm. It asks for the next greater integer using the same digits.
LeetCode 739 ➔ Daily Temperatures: A practical application. Instead of the value, you return the distance (indices) to the next greater element.
LeetCode 84 ➔ Largest Rectangle in Histogram: An L5 staple. Uses NGE logic (specifically Previous/Next Smaller Element) to find the width of the rectangle a bar can sustain.

These problems test the lexicographical logic, ranking, and inversions.

LeetCode 31 ➔ Next Permutation: The core problem discussed. Implement the pivot-swap-reverse logic.
LeetCode 60 ➔ Permutation Sequence: Finds the K-th Permutation. Requires the Factoradic (factorial number system) approach rather than iterative calls.
LeetCode 267 ➔ Palindrome Permutation II: Combines permutation logic with backtracking. You must generate all unique palindromic permutations.
LintCode 51 ➔ Previous Permutation: Inverts the logic to find the largest permutation smaller than the current one. Excellent for testing symmetry in your logic.

These problems move toward tree structures or complex constraints often seen in L5 interviews.

LeetCode 98 ➔ Validate Binary Search Tree: While seemingly unrelated, the NGE in a BST is its In-order Successor. This tests the connection between linear arrays and tree topologies.
LeetCode 316 ➔ Remove Duplicate Letters: Uses a monotonic stack to maintain Lexicographical Order while satisfying the constraint that every character must appear exactly once.
LeetCode 402 ➔ Remove K Digits: Uses a monotonic stack to find the smallest possible number. This tests the "minimal lexicographical decrease" logic.
LeetCode 1856 ➔ Maximum Subarray Min-Product: A "harder" variant of the Histogram problem. Uses NGE logic to define the range where an element is the minimum.