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[LeetCode] 981. Time Based Key-Value Store

Design a time-based key-value data structure that can store multiple values for the same key at different time stamps and retrieve the key’s value at a certain timestamp. Implement the TimeMap class:

2020-05-16

#leetcode #hashmap #java #treemap #string #binary search #design

[LeetCode] 85. Maximal Rectangle

Given a rows x cols binary matrix filled with 0’s and 1’s, find the largest rectangle containing only 1’s and return its area. Example 1:Input: matrix = [ [“1”,”0”,”1”,”0”,”0”], [“1”,”0”,”1

2020-05-15

#leetcode #array #java #javascript #stack #monotonic stack

[LeetCode] 987. Vertical Order Traversal of a Binary Tree

Given the root of a binary tree, calculate the vertical order traversal of the binary tree. For each node at position (row, col), its left and right children will be at positions (row + 1, col - 1) an

2020-05-13

#leetcode #hashmap #java #tree #bfs

[LeetCode] 314. Binary Tree Vertical Order Traversal

Given the root of a binary tree, return the vertical order traversal of its nodes’ values. (i.e., from top to bottom, column by column). If two nodes are in the same row and column, the order should b

2020-05-13

#leetcode #hashmap #java #javascript #tree #bfs

[LeetCode] 1441. Build an Array With Stack Operations

You are given an integer array target and an integer n.You have an empty stack with the two following operations:“Push”: pushes an integer to the top of the stack.“Pop”: removes the integer on the top

2020-05-11

#leetcode #java #simulation

[LeetCode] 277. Find the Celebrity

Suppose you are at a party with n people labeled from 0 to n - 1 and among them, there may exist one celebrity. The definition of a celebrity is that all the other n - 1 people know the celebrity, but

2020-05-11

#leetcode #java #graph

[LeetCode] 997. Find the Town Judge

In a town, there are n people labeled from 1 to n. There is a rumor that one of these people is secretly the town judge. If the town judge exists, then:The town judge trusts nobody.Everybody (except f

2020-05-11

#leetcode #hashmap #java #graph

[LeetCode] 1249. Minimum Remove to Make Valid Parentheses

Given a string s of ‘(‘ , ‘)’ and lowercase English characters. Your task is to remove the minimum number of parentheses ( ‘(‘ or ‘)’, in any positions ) so that the resulting parentheses string is va

2020-05-08

#leetcode #java #string #stack

[LeetCode] 84. Largest Rectangle in Histogram

Given an array of integers heights representing the histogram’s bar height where the width of each bar is 1, return the area of the largest rectangle in the histogram. Example 1:Input: heights =

2020-05-08

#leetcode #array #java #javascript #stack #monotonic stack

[LeetCode] 993. Cousins in Binary Tree

Given the root of a binary tree with unique values and the values of two different nodes of the tree x and y, return true if the nodes corresponding to the values x and y in the tree are cousins, or f

2020-05-08

#leetcode #java #tree #bfs #dfs