ProgramCreek 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. Java Solution … Read more
Convert a non-negative integer to its english words representation. Given input is guaranteed to be less than 231 – 1. For example, 123 -> “One Hundred Twenty Three” 12345 -> “Twelve Thousand Three Hundred Forty Five” Java Solution This problem is straightforward, but the corner cases should be considered carefully. public class Solution { HashMap<Integer, … Read more
Given an input string, reverse the string word by word. A word is defined as a sequence of non-space characters. The input string does not contain leading or trailing spaces and the words are always separated by a single space. For example, Given s = “the sky is blue”, return “blue is sky the”. Could … Read more
Write a program to check whether a given number is an ugly number. Ugly numbers are positive numbers whose prime factors only include 2, 3, 5. For example, 6, 8 are ugly while 14 is not ugly since it includes another prime factor 7. Note that 1 is typically treated as an ugly number. Java … Read more
There is a fence with n posts, each post can be painted with one of the k colors. You have to paint all the posts such that no more than two adjacent fence posts have the same color. Return the total number of ways you can paint the fence. Java Solution The key to solve … Read more
There are n bulbs that are initially off. You first turn on all the bulbs. Then, you turn off every second bulb. On the third round, you toggle every third bulb (turning on if it’s off or turning off if it’s on). For the ith round, you toggle every i bulb. For the nth round, … Read more
You are a product manager and currently leading a team to develop a new product. Unfortunately, the latest version of your product fails the quality check. Since each version is developed based on the previous version, all the versions after a bad version are also bad. Suppose you have n versions [1, 2, …, n] … Read more
Given two strings s1 and s2 of the same length, determine if s2 is a scrambled string of s1. Java Solution public boolean isScramble(String s1, String s2) { if(s1.length()!=s2.length()) return false; if(s1.length()==0 || s1.equals(s2)) return true; char[] arr1 = s1.toCharArray(); char[] arr2 = s2.toCharArray(); Arrays.sort(arr1); Arrays.sort(arr2); if(!new String(arr1).equals(new String(arr2))){ return false; } … Read more
Given two strings S and T, determine if they are both one edit distance apart. Java Solution public boolean isOneEditDistance(String s, String t) { if(s==null || t==null) return false; int m = s.length(); int n = t.length(); if(Math.abs(m-n)>1){ return false; } int i=0; int j=0; int count=0; while(i<m&&j<n){ if(s.charAt(i)==t.charAt(j)){ i++; j++; … Read more
Given a list of unique words. Find all pairs of distinct indices (i, j) in the given list, so that the concatenation of the two words, i.e. words[i] + words[j] is a palindrome. Example 1: Given words = [“bat”, “tab”, “cat”] Return [[0, 1], [1, 0]] The palindromes are [“battab”, “tabbat”] Java Solution public List<List<Integer>> … Read more
Given a positive integer n, find the least number of perfect square numbers (for example, 1, 4, 9, 16, …) which sum to n. For example, given n = 12, return 3 because 12 = 4 + 4 + 4; given n = 13, return 2 because 13 = 4 + 9. Java Solution This … Read more
Reverse a singly linked list. Java Solution 1 – Iterative public ListNode reverseList(ListNode head) { if(head==null||head.next==null) return head; ListNode p1 = head; ListNode p2 = p1.next; head.next = null; while(p1!=null&& p2!=null){ ListNode t = p2.next; p2.next = p1; p1 = p2; p2 = t; } return p1; }public ListNode reverseList(ListNode head) { … Read more
Given two strings s and t, determine if they are isomorphic. Two strings are isomorphic if the characters in s can be replaced to get t. For example,”egg” and “add” are isomorphic, “foo” and “bar” are not. Java Solution 1 We can define a map which tracks the char-char mappings. If a value is already … Read more
There are a total of n courses you have to take, labeled from 0 to n – 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, … Read more
Given a board with m by n cells, each cell has an initial state live (1) or dead (0). Each cell interacts with its eight neighbors (horizontal, vertical, diagonal) using the following four rules: Any live cell with fewer than two live neighbors dies, as if caused by under-population. Any live cell with two or … Read more