Problem Given a positive integer, return its corresponding column title as appear in an Excel sheet. For example: 1 -> A 2 -> B 3 -> C … 26 -> Z 27 -> AA 28 -> AB Java Solution This problem is the reverse version of Excel Sheet Column Number. The key is n–. The … Read more
Problem Given a column title as appear in an Excel sheet, return its corresponding column number. For example: A -> 1 B -> 2 C -> 3 … Z -> 26 AA -> 27 AB -> 28 … AAA -> 703 Java Solution This problem is related to Excel Sheet Column Title. public int titleToNumber(String … Read more
There are N gas stations along a circular route, where the amount of gas at station i is gas[i]. You have a car with an unlimited gas tank and it costs cost[i] of gas to travel from station i to its next station (i+1). You begin the journey with an empty tank at one of … Read more
Problem Given an array of integers, every element appears three times except for one. Find that single one. Java Solution This problem is similar to Single Number. public int singleNumber(int[] A) { int ones = 0, twos = 0, threes = 0; for (int i = 0; i < A.length; i++) { twos |= ones … Read more
Problem Compare two version numbers version1 and version2. If version1 > version2 return 1, if version1 < version2 return -1, otherwise return 0. You may assume that the version strings are non-empty and contain only digits and the . character. The . character does not represent a decimal point and is used to separate number ... Read more
Given a string s and a dictionary of words dict, add spaces in s to construct a sentence where each word is a valid dictionary word. Return all such possible sentences. For example, given s = “catsanddog”, dict = [“cat”, “cats”, “and”, “sand”, “dog”], the solution is [“cats and dog”, “cat sand dog”]. Java Solution … Read more
Find the contiguous subarray within an array (containing at least one number) which has the largest product. For example, given the array [2,3,-2,4], the contiguous subarray [2,3] has the largest product = 6. Java Solution – Dynamic Programming This is similar to maximum subarray. Instead of sum, the sign of number affect the product value. … Read more
Follow up for “Find Minimum in Rotated Sorted Array”: What if duplicates are allowed? Would this affect the run-time complexity? How and why? Java Solution 1 – Recursion This is a follow-up problem of finding minimum element in rotated sorted array without duplicate elements. We only need to add one more condition, which checks if … Read more
Given two integers n and k, return all possible combinations of k numbers out of 1 … n. For example, if n = 4 and k = 2, a solution is: [ [2,4], [3,4], [2,3], [1,2], [1,3], [1,4], ] Java Solution public ArrayList<ArrayList<Integer>> combine(int n, int k) { ArrayList<ArrayList<Integer>> result = new ArrayList<ArrayList<Integer>>(); if … Read more
Given a list of non negative integers, arrange them such that they form the largest number. For example, given [3, 30, 34, 5, 9], the largest formed number is 9534330. (Note: The result may be very large, so you need to return a string instead of an integer.) Analysis This problem can be solved by … Read more
Problem Write a program to find the node at which the intersection of two singly linked lists begins. For example, the following two linked lists: A: a1 -> a2 -> c1 -> c2 -> c3 -> B: b1 -> b2 -> b3 begin to intersect at node c1. Java Solution First calculate the length of … Read more
Problem Write a function to find the longest common prefix string amongst an array of strings. Analysis To solve this problem, we need to find the two loop conditions. One is the length of the shortest string. The other is iteration over every element of the string array. Java Solution public String longestCommonPrefix(String[] strs) { … Read more
Design and implement a data structure for Least Recently Used (LRU) cache, which supports get and put. Analysis The key to solve this problem is using a double linked list which enables us to quickly move nodes. The LRU cache is a hash table of keys and double linked nodes. The hash table makes the … Read more
Problem Given a string s, partition s such that every substring of the partition is a palindrome. Return all possible palindrome partitioning of s. For example, given s = “aab”, Return [ [“aa”,”b”], [“a”,”a”,”b”] ] 1. Depth-first Search public ArrayList<ArrayList<String>> partition(String s) { ArrayList<ArrayList<String>> result = new ArrayList<ArrayList<String>>(); if (s == null || s.length() … Read more
