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grind75

A collection of 37 posts

141. Linked List Cycle

141. Linked List Cycle

❤️ I love the algorithm used here! Problem Given head, the head of a linked list, determine if the linked list has a cycle in it. There is a cycle in a linked list if there is some node in the list that can be reached again by continuously following the

235. Lowest Common Ancestor of a Binary Search Tree

235. Lowest Common Ancestor of a Binary Search Tree

Problem Given a binary search tree (BST), find the lowest common ancestor (LCA) node of two given nodes in the BST. According to the definition of LCA on Wikipedia: “The lowest common ancestor is defined between two nodes p and q as the lowest node in T that has both

104. Maximum Depth of Binary Tree

104. Maximum Depth of Binary Tree

Submission Given the root of a binary tree, return its maximum depth. A binary tree's maximum depth is the number of nodes along the longest path from the root node down to the farthest leaf node. Example 1: Input: root = [3,9,20,null,null,15,7] Output:

110. Balanced Binary Tree

110. Balanced Binary Tree

Problem Given a binary tree, determine if it is height-balanced. Example 1: Input: root = [3,9,20,null,null,15,7] Output: true Example 2: Input: root = [1,2,2,3,3,null,null,4,4] Output: false Example 3: Input: root = [] Output: true Solution # Definition for a binary tree

232. Implement Queue using Stacks

232. Implement Queue using Stacks

Problem Implement a first in first out (FIFO) queue using only two stacks. The implemented queue should support all the functions of a normal queue (push, peek, pop, and empty). Implement the MyQueue class: * void push(int x) Pushes element x to the back of the queue. * int pop() Removes

704. Binary Search

704. Binary Search

Problem Given an array of integers nums which is sorted in ascending order, and an integer target, write a function to search target in nums. If target exists, then return its index. Otherwise, return -1. You must write an algorithm with O(log n) runtime complexity. Example 1: Input: nums

242. Valid Anagram

242. Valid Anagram

Problem Given two strings s and t, return true if t is an anagram of s, and false otherwise. An Anagram is a word or phrase formed by rearranging the letters of a different word or phrase, typically using all the original letters exactly once. Example 1: Input: s = "

226. Invert Binary Tree

226. Invert Binary Tree

❤️ This is one of my favourite leetcode problems. I was in a 1v1 race against someone and I came up with the solution without knowing how to do it, I felt so estatic when my code worked first time! Problem Given the root of a binary tree, invert the tree,

121. Best Time to Buy and Sell Stock

121. Best Time to Buy and Sell Stock

Problem You are given an array prices where prices[i] is the price of a given stock on the ith day. You want to maximize your profit by choosing a single day to buy one stock and choosing a different day in the future to sell that stock. Return the

125. Valid Palindrome

Problem A phrase is a palindrome if, after converting all uppercase letters into lowercase letters and removing all non-alphanumeric characters, it reads the same forward and backward. Alphanumeric characters include letters and numbers. Given a string s, return true if it is a palindrome, or false otherwise. Example 1: Input:

21. Merge Two Sorted Lists

21. Merge Two Sorted Lists

Problem You are given the heads of two sorted linked lists list1 and list2. Merge the two lists in a one sorted list. The list should be made by splicing together the nodes of the first two lists. Return the head of the merged linked list. Example 1: Input: list1

Grind75-2 - Valid Parathesis

Grind75-2 - Valid Parathesis

Problem Given a string s containing just the characters '(', ')', '{', '}', '[' and ']', determine if the input string is valid. An input string is valid if: 1. Open brackets must be closed by the same type of brackets. 2. Open brackets