Problem Given a binary tree, write an algorithm for postorder traversal. Postorder Traversal Visit all the nodes in the left subtree Visit all the nodes in the right subtree Visit the root node postorder(root->left) postorder(root->right) display(root->data) Examples Example 1: 1 \ 2 / 3 ...
Problem Implement an algorithm to print all valid (i.e., properly opened and closed) combinations of n-pairs of parentheses. OR Given n pairs of parentheses, write a function to generate all combinations of well-formed parentheses. Follow up Make sure the returned list of strings are sorted. Examples Example 1: Input: n = 3 Output: ["((()))","(()())","(())()","()(())","()()()"] ...
Problem Given a binary tree, find the diameter of it. Definition Diameter of tree is defined as a longest path or route between any two nodes in a tree. The path may or may not for through the root. Example Example 1: 1 / \ 2 3 / \ 4 5 Input: root = [1,2,3,4,5] Output: 3 Explanation: 3 is the length of the path [4,2,1,3] or [5,2,1,3]. ...
Problem Given head, the head of a linked list, determine if the linked list has a cycle in it. Return true if there is a cycle in the linked list. Otherwise, return false. Examples Example 1 Input: head = [0, 1, 3, 2, 4] output: true Explanation: Cycle starts at node 2 ...
Problem There are n children standing in a line. Each child is assigned a rating value given in the integer array ratings. You are giving candies to these children subjected to the following requirements: Each child must have at least one candy. Children with a higher rating get more candies than their neighbors. Return the minimum number of candies you need to have to distribute the candies to the children. ...
Problem Given a string s, return the longest palindromic substring in s. Incase of conflict, return the substring which occurs first ( with the least starting index ). Substring of string S: S[i...j] where 0 <= i <= j < len(S) Example Example 1: Input: s = "babad" Output: "bab" Explanation: "aba" is also a valid answer. ...
Problem Implement the myAtoi(string s) function, which converts a string to a 32-bit signed integer. The algorithm for myAtoi(string s) is as follows: Whitespace: Ignore any leading whitespace (" "). Signedness: Determine the sign by checking if the next character is '-' or '+', assuming positivity is neither present. Conversion: Read the integer by skipping leading zeros until a non-digit character is encountered or the end of the string is reached. If no digits were read, then the result is 0. Rounding: If the integer is out of the 32-bit signed integer range [-2^31, 2^31 - 1], then round the integer to remain in the range. Specifically, integers less than -2^31 should be rounded to -2^31, and integers greater than 2^31 - 1 should be rounded to 2^31 - 1. Return the integer as the final result. ...
Problem Given an array nums of size n, return the majority element. The majority element is the element that appears more than ⌊n / 2⌋ times. You may assume that the majority element always exists in the array. Definition Majority Element: If an element appears more than n/2 times in array where n is the size of the array. Examples int [] arrA = {1,3,5,5,5,5,4,1,5}; Output: Element appearing more than n/2 times: 5 int []arrA = {1,2,3,4}; Output: No element appearing more than n/2 times ...
Problem Given two sorted arrays nums1 and nums2 of size m and n respectively, return the median of the two sorted arrays. The overall run time complexity should be O(log (m+n)). Examples Example 1: Input: nums1 = [1,3], nums2 = [2] Output: 2.00000 Explanation: merged array = [1,2,3] and median is 2. ...
Problem Given an m x n matrix of 0s and 1s, provide an algorithm such that if an element is 0, its entire row and column is set to 0 OR Given an m x n integer matrix matrix, if an element is 0, set its entire row and column to 0’s. You must do it in place. Follow Up: Can you do it in one pass? ...