LeetCode 232. Implement Queue using Stacks
Description https://leetcode.com/problems/implement-queue-using-stacks/ Implement a first in first out (FIFO) queue using only two stacks. The implemented queue should support all…
Category: Stack
LeetCode 225. Implement Stack using Queues
Description https://leetcode.com/problems/implement-queue-using-stacks/ Implement a last in first out (LIFO) stack using only two queues. The implemented stack should support all…
LeetCode 394. Decode String
Description https://leetcode.com/problems/decode-string/ Given an encoded string, return its decoded string. The encoding rule is: k[encoded_string], where the encoded_string inside the square brackets is…
LeetCode 895. Maximum Frequency Stack
Description https://leetcode.com/problems/maximum-frequency-stack/ Implement FreqStack, a class which simulates the operation of a stack-like data structure. FreqStack has two functions: push(int x), which…
LeetCode 678. Valid Parenthesis String
Description https://leetcode.com/problems/valid-parenthesis-string/ Given a string containing only three types of characters: ‘(‘, ‘)’ and ‘*’, write a function to check…
LeetCode 268. Missing Number
Description https://leetcode.com/problems/missing-number/ Given an array containing n distinct numbers taken from 0, 1, 2, …, n, find the one that is missing from…
LeetCode 844. Backspace String Compare
Description https://leetcode.com/problems/backspace-string-compare/ Given two strings S and T, return if they are equal when both are typed into empty text editors. # means a backspace character. Example…
LeetCode 84. Largest Rectangle in Histogram
Description https://leetcode.com/problems/largest-rectangle-in-histogram/description/ Given n non-negative integers representing the histogram’s bar height where the width of each bar is 1, find the area…
LeetCode 155. Min Stack
Description Design a stack that supports push, pop, top, and retrieving the minimum element in constant time. push(x) — Push…
LeetCode 20. Valid Parentheses
Description https://leetcode.com/problems/valid-parentheses/ Given a string s containing just the characters ‘(‘, ‘)’, ‘{‘, ‘}’, ‘[‘ and ‘]’, determine if the input string is valid. An input string is valid…