here are a row of n houses, each house can be painted with one of the three colors: red, blue or green. The cost of painting each house with a certain color is different. You have to paint all the houses such that no two adjacent houses have the same color. The […]
Closest Binary Search Tree Value II Given a non-empty binary search tree and a target value, find k values in the BST that are closest to the target. Note: Given target value is a floating point. You may assume k is always valid, that is: k ≤ total nodes. You are guaranteed to have only one […]
Add Digits Given a non-negative integer num, repeatedly add all its digits until the result has only one digit. For example: Given num = 38, the process is like: 3 + 8 = 11, 1 + 1 = 2. Since 2 has only one digit, return it. Follow up: Could you do it without any loop/recursion […]
Write a program to find the n-th ugly number. Ugly numbers are positive numbers whose prime factors only include 2, 3, 5. For example, 1, 2, 3, 4, 5, 6, 8, 9, 10, 12 is the sequence of the first 10 ugly numbers. Note that 1 is typically treated as an ugly number. Hint: The naive approach is […]
Motivation The difference between threads and processes used to confused me. Why do we need threads since we already have processes to support concurrency? What’s the mechanism of the context switch between threads?(rather than processes) How is locks implemented? This article may be your answer. Acknowledgement: Some of the sentences […]
Maximal Square Given a 2D binary matrix filled with 0’s and 1’s, find the largest square containing all 1’s and return its area. For example, given the following matrix: 1 0 1 0 0 1 0 1 1 1 1 1 1 1 1 1 0 0 1 0 Return […]
Unique Word Abbreviation An abbreviation of a word follows the form <first letter><number><last letter>. Below are some examples of word abbreviations: a) it –> it (no abbreviation) 1 b) d|o|g –> d1g 1 1 1 1—5—-0—-5–8 c) i|nternationalizatio|n –> i18n 1 1—5—-0 d) l|ocalizatio|n –> l10n Assume you have a […]
Palindrome Permutation II Given a string s, return all the palindromic permutations (without duplicates) of it. Return an empty list if no palindromic permutation could be form. For example: Given s = “aabb”, return [“abba”, “baab”]. Given s = “abc”, return []. First, count the frequency of the each character […]
Given an array nums containing n + 1 integers where each integer is between 1 and n (inclusive), prove that at least one duplicate number must exist. Assume that there is only one duplicate number, find the duplicate one. Note: You must not modify the array (assume the array is […]
H-Index Given an array of citations (each citation is a non-negative integer) of a researcher, write a function to compute the researcher’s h-index. According to the definition of h-index on Wikipedia: “A scientist has index h if h of his/her N papers have at leasth citations each, and the other […]
