ProgramCreek Given a sorted array of integers, find the starting and ending position of a given target value. Your algorithm’s runtime complexity must be in the order of O(log n). If the target is not found in the array, return [-1, -1]. For example, given [5, 7, 7, 8, 8, 10] and target value 8, return … Read more
Given an array of strings, return all groups of strings that are anagrams. An anagram is a type of word play, the result of rearranging the letters of a word or phrase to produce a new word or phrase, using all the original letters exactly once; for example, Torchwood can be rearranged into Doctor Who. … Read more
Given a 2D matrix matrix, find the sum of the elements inside the rectangle defined by its upper left corner (row1, col1) and lower right corner (row2, col2). Analysis Since the assumption is that there are many calls to sumRegion method, we should use some extra space to store the intermediate results. The solution is … Read more
Given a collection of candidate numbers (C) and a target number (T), find all unique combinations in C where the candidate numbers sums to T. Each number in C may only be used ONCE in the combination. Note: 1) All numbers (including target) will be positive integers. 2) Elements in a combination (a1, a2, … … Read more
Given a binary tree, return the bottom-up level order traversal of its nodes’ values. For example, given binary tree {3,9,20,#,#,15,7}, 3 / \ 9 20 / \ 15 7 return its level order traversal as [[15,7], [9,20],[3]] Java Solution public List<ArrayList<Integer>> levelOrderBottom(TreeNode root) { ArrayList<ArrayList<Integer>> result = new ArrayList<ArrayList<Integer>>(); if(root == null){ return result; … Read more
Given a binary tree, return the level order traversal of its nodes’ values. (ie, from left to right, level by level). For example: Given binary tree {3,9,20,#,#,15,7}, 3 / \ 9 20 / \ 15 7 return its level order traversal as [[3], [9,20], [15,7]] Java Solution 1 It is obvious that this problem can … Read more
Given an array and a value, remove all instances of that value in place and return the new length. (Note: The order of elements can be changed. It doesn’t matter what you leave beyond the new length.) Java Solution This problem can be solve by using two indices. public int removeElement(int[] A, int elem) { … Read more
Given a digit string, return all possible letter combinations that the number could represent. (Check out your cellphone to see the mappings) Input:Digit string “23”, Output: [“ad”, “ae”, “af”, “bd”, “be”, “bf”, “cd”, “ce”, “cf”]. Java Solution 1 – DFS This problem can be solves by a typical DFS algorithm. DFS problems are very similar … Read more
Write an algorithm to determine if a number is “happy”. What is an happy number can be shown in the following example: 19 is a happy number 1^2 + 9^2 = 82 8^2 + 2^2 = 68 6^2 + 8^2 = 100 1^2 + 0^2 + 0^2 = 1 Analysis The key to solve this … Read more
Remove all elements from a linked list of integers that have value val. Example Given: 1 –> 2 –> 6 –> 3 –> 4 –> 5 –> 6, val = 6 Return: 1 –> 2 –> 3 –> 4 –> 5 Java Solution The key to solve this problem is using a helper node to … Read more
Given a 2D board containing ‘X’ and ‘O’, capture all regions surrounded by ‘X’. A region is captured by flipping all ‘O’s into ‘X’s in that surrounded region. For example, X X X X X O O X X X O X X O X X After running your function, the board should be: X … Read more
Given an index k, return the kth row of the Pascal’s triangle. For example, when k = 3, the row is [1,3,3,1]. Analysis This problem is related to Pascal’s Triangle which gets all rows of Pascal’s triangle. In this problem, only one row is required to return. Java Solution public List<Integer> getRow(int rowIndex) { ArrayList<Integer> … Read more
Given a string s, partition s such that every substring of the partition is a palindrome. Return the minimum cuts needed for a palindrome partitioning of s. For example, given s = “aab”, return 1 since the palindrome partitioning [“aa”,”b”] could be produced using 1 cut. Analysis This problem is similar to Palindrome Partitioning. It … Read more
Given a range [m, n] where 0
Given n points on a 2D plane, find the maximum number of points that lie on the same straight line. Analysis This problem can be solve by counting points that have the same slope for each point. When counting, we need to be careful about the duplicate points and points on the vertical lines. Java … Read more