#LeetCode: Rotting Oranges

Also Check: August LeetCoding Challenge (2020)

In a given grid, each cell can have one of three values:

the value 0 representing an empty cell;
the value 1 representing a fresh orange;
the value 2 representing a rotten orange.
Every minute, any fresh orange that is adjacent (4-directionally) to a rotten orange becomes rotten.

Return the minimum number of minutes that must elapse until no cell has a fresh orange.  If this is impossible, return -1 instead.

#LeetCode: Path Sum III

Also Check: August LeetCoding Challenge (2020)

You are given a binary tree in which each node contains an integer value.

Find the number of paths that sum to a given value.

The path does not need to start or end at the root or a leaf, but it must go downwards (traveling only from parent nodes to child nodes).

#LeetCode: Add and Search Word - Data structure design

Design a data structure that supports the following two operations:

• void addWord(word)
• bool search(word)

search(word) can search a literal word or a regular expression string containing only letters a-z or .. A . means it can represent any one letter.

#LeetCode: Power of Four

Also Check: August LeetCoding Challenge (2020)

Given an integer (signed 32 bits), write a function to check whether it is a power of 4.

Example 1:
Input: 16
Output: true

#LeetCode: Valid Palindrome

Also Check: August LeetCoding Challenge (2020)

Given a string, determine if it is a palindrome, considering only alphanumeric characters and ignoring cases.

Note: For the purpose of this problem, we define empty string as valid palindrome.

Example 1:
Input: "A man, a plan, a canal: Panama"
Output: true

Example 2:
Input: "race a car"
Output: false

#LeetCode: Design HashSet

Also Check: August LeetCoding Challenge (2020)

Design a HashSet without using any built-in hash table libraries.

To be specific, your design should include these functions:

• add(value): Insert a value into the HashSet. 
• contains(value) : Return whether the value exists in the HashSet or not.
• remove(value): Remove a value in the HashSet. If the value does not exist in the HashSet, do nothing.

#LeetCode : Detect Capital

Also Check: August LeetCoding Challenge (2020)

Given a word, you need to judge whether the usage of capitals in it is right or not.

We define the usage of capitals in a word to be right when one of the following cases holds:

• All letters in this word are capitals, like "USA".
• All letters in this word are not capitals, like "leetcode".
• Only the first letter in this word is capital, like "Google".
• Otherwise, we define that this word doesn't use capitals in a right way.

How to implement Snakes and Ladders using Java?

ALSO CHECK: Algorithms and System Design Interview Questions

Let's create a SnakeNLadder.java class. Define constant WINPOINT with value 100. Each player has to start the journey from 0, roll the dice and try to reach WINPOINT.

#LeetCode : Power Of Two

Also Check: June LeetCoding Challenge (2020)

Given an integer, write a function to determine if it is a power of two.

Example 1:

Input: 1
Output: true 
Explanation: 20 = 1

#LeetCode : Coin Change 2

Also Check: June LeetCoding Challenge (2020)

You are given coins of different denominations and a total amount of money. Write a function to compute the number of combinations that make up that amount. You may assume that you have infinite number of each kind of coin.

Example 1:
Input: amount = 5, coins = [1, 2, 5]
Output: 4
Explanation: there are four ways to make up the amount:
5=5
5=2+2+1
5=2+1+1+1
5=1+1+1+1+1

#LeetCode :Queue Reconstruction by Height

Also Check: June LeetCoding Challenge (2020)

Suppose you have a random list of people standing in a queue. Each person is described by a pair of integers (h, k), where h is the height of the person and k is the number of people in front of this person who have a height greater than or equal to h. Write an algorithm to reconstruct the queue.

Note:
The number of people is less than 1,100.

Example
Input:[[7,0], [4,4], [7,1], [5,0], [6,1], [5,2]]
Output:[[5,0], [7,0], [5,2], [6,1], [4,4], [7,1]]

#LeetCode : Reverse String

Also Check: June LeetCoding Challenge (2020)

Write a function that reverses a string. The input string is given as an array of characters char[].

Do not allocate extra space for another array, you must do this by modifying the input array in-place with O(1) extra memory.

You may assume all the characters consist of printable ascii characters.

#LeetCode : Two City Scheduling

Also Check: June LeetCoding Challenge (2020)

There are 2N people a company is planning to interview. The cost of flying the i-th person to city A is costs[i][0], and the cost of flying the i-th person to city B is costs[i][1].

Return the minimum cost to fly every person to a city such that exactly N people arrive in each city.

Example 1:
Input: [[10,20],[30,200],[400,50],[30,20]]
Output: 110
Explanation:
The first person goes to city A for a cost of 10.
The second person goes to city A for a cost of 30.
The third person goes to city B for a cost of 50.
The fourth person goes to city B for a cost of 20.

The total minimum cost is 10 + 30 + 50 + 20 = 110 to have half the people interviewing in each city.

#LeetCode Delete Node in a Linked List

Also Check: June LeetCoding Challenge (2020)

Write a function to delete a node (except the tail) in a singly linked list, given only access to that node.

Example 1:
Input: head = [4,5,1,9], node = 5
Output: [4,1,9]
Explanation: You are given the second node with value 5, the linked list should become 4 -> 1 -> 9 after calling your function.

#LeetCode: Invert Binary Tree

Also Check: June LeetCoding Challenge (2020)

Invert the given Binary tree

#LeetCode: Edit Distance

Also Check: Solutions Of May LeetCoding Challenge (2020)

Given two words word1 and word2, find the minimum number of operations required to convert word1 to word2.

You have the following 3 operations permitted on a word:

• Insert a character
• Delete a character
• Replace a character

#LeetCode: K Closest Points to Origin

Also Check: Solutions Of May LeetCoding Challenge (2020)

We have a list of points on the plane.  Find the K closest points to the origin (0, 0).(Here, the distance between two points on a plane is the Euclidean distance.)

You may return the answer in any order.  The answer is guaranteed to be unique (except for the order that it is in.)

#LeetCode: Course Schedule

Also Check: Solutions Of May LeetCoding Challenge (2020)

There are a total of numCourses courses you have to take, labeled from 0 to numCourses-1.

Some courses may have prerequisites, for example to take course 0 you have to first take course 1, which is expressed as a pair: [0,1]

Given the total number of courses and a list of prerequisite pairs, is it possible for you to finish all courses?

Example 1:
Input: numCourses = 2, prerequisites = [[1,0]]
Output: true
Explanation: There are a total of 2 courses to take.
             To take course 1 you should have finished course 0. So it is possible.

Example 2:
Input: numCourses = 2, prerequisites = [[1,0],[0,1]]
Output: false
Explanation: There are a total of 2 courses to take.
             To take course 1 you should have finished course 0, and to take course 0 you should
             also have finished course 1. So it is impossible.

Constraints:
The input prerequisites is a graph represented by a list of edges, not adjacency matrices. Read more about how a graph is represented.
You may assume that there are no duplicate edges in the input prerequisites.
1 <= numCourses <= 10^5

GIT URL: Java Solution of Leet Code's Course Schedule problem

Java Solution 1

ALSO CHECK: Other LeetCode Solutions in Java

-K Himaanshu Shuklaa.

#LeetCode: Counting Bits

Also Check: Solutions Of May LeetCoding Challenge (2020)

Given a non negative integer number num. For every numbers i in the range 0 ≤ i ≤ num calculate the number of 1's in their binary representation and return them as an array.

Example 1:
Input: 2
Output: [0,1,1]

Example 2:
Input: 5
Output: [0,1,1,2,1,2]

#LeetCode: Possible Bipartition

Also Check: Solutions Of May LeetCoding Challenge (2020)

Given a set of N people (numbered 1, 2, ..., N), we would like to split everyone into two groups of any size.

Each person may dislike some other people, and they should not go into the same group.

Formally, if dislikes[i] = [a, b], it means it is not allowed to put the people numbered a and b into the same group.

Return true if and only if it is possible to split everyone into two groups in this way.