LeetCode Problem Solving Log

Given a Binary Search Tree and a target number, return true if there exist two elements in the BST s…

Given a binary tree and a sum, determine if the tree has a root-to-leaf path such that adding up all…

Given a binary tree, determine if it is height-balanced. For this problem, a height-balanced binary …

Given a non-empty binary search tree and a target value, find the value in the BST that is closest t…

Given two binary trees, write a function to check if they are equal or not. Two binary trees are con…

Given a binary tree, return the bottom-up level order traversal of its nodes’ values. (ie, fro…

Given a binary tree, return all root-to-leaf paths. For example, given the following binary tree: 1 …

Find the nth digit of the infinite integer sequence 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, … Note:…

The set S originally contains numbers from 1 to n. But unfortunately, due to the data error, one of …

Write an algorithm to determine if a number is “happy”. A happy number is a number defin…

Given a non-negative integer num, repeatedly add all its digits until the result has only one digit.…

You have a total of n coins that you want to form in a staircase shape, where every k-th row must ha…

Given a positive integer, return its corresponding column title as appear in an Excel sheet. For exa…

Given an integer, write a function to determine if it is a power of two. class Solution { public boo…

Write a program to check whether a given number is an ugly number. Ugly numbers are positive numbers…