Topic: Stack-question / Level: Advanced

• 401. Implement a function to find the smallest element in a stack in O(1) time.
• 402. Write a function to reverse a stack using recursion.
• 403. Implement a stack that supports push, pop, top, and retrieving the minimum element in constant time.
• 404. Write a function to evaluate a mathematical expression in postfix notation with error handling.
• 405. Implement a function to sort a stack using another stack.
• 406. Write a function to check if a stack is a permutation of another stack.
• 407. Implement a function to find the longest valid parentheses substring in a string using a stack.
• 408. Write a function to implement a priority stack that retrieves the highest priority item.
• 409. Implement a function to calculate the maximum depth of nested parentheses.
• 410. Write a function to implement a two-stack queue.
• 411. Implement a function to check if a stack can be sorted with a limited number of auxiliary stacks.
• 412. Write a function to create a stack that keeps track of the maximum element.
• 413. Implement a function to find the longest common subsequence between two strings using a stack.
• 414. Write a function to implement a min-max stack.
• 415. Implement a function to find all valid combinations of parentheses using a stack.
• 416. Write a function to detect a cycle in a stack representation of a linked list.
• 417. Implement a function to evaluate infix expressions using the Shunting Yard algorithm.
• 418. Write a function to check if a stack is a palindrome.
• 419. Implement a function to merge K sorted stacks into a single sorted stack.
• 420. Write a function to find the shortest valid parentheses substring.
• 421. Implement a function to implement a stack that supports duplicate elements while maintaining order.
• 422. Write a function to find the longest substring without repeating characters using a stack.
• 423. Implement a function to create a stack that supports range queries.
• 424. Write a function to find the number of ways to arrange parentheses.
• 425. Implement a function to find the maximum area of a rectangle in a histogram using a stack.
• 426. Write a function to evaluate a complex expression with nested operations.
• 427. Implement a function to check if a string is a valid serialization of a binary tree using a stack.
• 428. Write a function to calculate the longest increasing subsequence in a stack.
• 429. Implement a function to generate all possible permutations of a stack using backtracking.
• 430. Write a function to find the maximum difference between the top two elements of a stack.

• More Levels

• Beginner
• Intermediate