Stack - Michael's Blog

Stack

A collection of 7 posts

Binary Tree Preorder Traversal

144. Binary Tree Preorder Traversal [https://leetcode.com/problems/binary-tree-preorder-traversal/?tab=Description] Given a binary tree, return the preorder traversal of its nodes' values. For example: Given binary tree {1,#,2,3}, 1 \ 2 / 3 return [1,2,3]. Note: Recursive solution is trivial, could you do it iteratively? class

Binary Tree Inorder Traversal

94. Binary Tree Inorder Traversal [http://www.lintcode.com/en/problem/binary-tree-inorder-traversal] Given a binary tree, return the inorder traversal of its nodes' values. For example: Given binary tree [1,null,2,3], 1 \ 2 / 3 return [1,3,2]. Note: Recursive solution is trivial, could you do it iteratively?

Basic Calculator

224. Basic Calculator [https://leetcode.com/problems/basic-calculator/] Implement a basic calculator to evaluate a simple expression string. The expression string may contain open ( and closing parentheses ), the plus + or minus sign -, non-negative integers and empty spaces . You may assume that the given expression is always valid. Some examples:

Decode String

394. Decode String [https://leetcode.com/problems/decode-string/description/] Given an encoded string, return it's decoded string. The encoding rule is: k[encoded_string], where the encoded_string inside the square brackets is being repeated exactly k times. Note that k is guaranteed to be a positive integer. You may

Stack Sorting

LintCode-229.Stack Sorting [http://www.lintcode.com/en/problem/stack-sorting] > Sort a stack in ascending order (with biggest terms on top). > You may use at most one additional stack to hold items, but you may not copy the elements into any other data structure (e.g. array). > Given stack = | | |3|

Implement Queue by Two Stacks

LintCode-40.Implement Queue by Two Stacks [http://www.lintcode.com/en/problem/implement-queue-by-two-stacks/] > As the title described, you should only use two stacks to implement a queue's actions. > The queue should support push(element), pop() and top() where pop is pop the first(a.k.a front) element in the

Implement Stack by Two Queues

LintCode-494.Implement Stack by Two Queues [http://www.lintcode.com/en/problem/implement-stack-by-two-queues/] > Implement a stack by two queues. The queue is first in first out (FIFO). That means you can not directly pop the last element in a queue. For this question, you need to pay attention to the