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[LeetCode] 1277. Count Square Submatrices with All Ones

Given a m * n matrix of ones and zeros, return how many square submatrices have all ones. Example 1:Input: matrix =[ [0,1,1,1], [1,1,1,1], [0,1,1,1]]Output: 15Explanation:There are 10 squares

2020-05-22

#leetcode #java #dynamic programming #matrix

[LeetCode] 901. Online Stock Span

Design an algorithm that collects daily price quotes for some stock and returns the span of that stock’s price for the current day. The span of the stock’s price in one day is the maximum number of co

2020-05-20

#leetcode #java #design #stack #monotonic stack

[LeetCode] 1371. Find the Longest Substring Containing Vowels in Even Counts

Given the string s, return the size of the longest substring containing each vowel an even number of times. That is, ‘a’, ‘e’, ‘i’, ‘o’, and ‘u’ must appear an even number of times. Example 1:Input: s

2020-05-20

#leetcode #java #prefix sum #string #bit manipulation

[LeetCode] 567. Permutation in String

Given two strings s1 and s2, return true if s2 contains a permutation of s1, or false otherwise. In other words, return true if one of s1’s permutations is the substring of s2. Example 1:Input: s1 &#x

2020-05-19

#leetcode #two pointer #hashmap #java #sliding window #string

[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