Problem Given two integer arrays inorder and postorder where inorder is the inorder traversal of a binary tree and postorder is the postorder traversal of the same tree, construct and return the binary tree. Example Example 1: 3 / \ 9 20 / \ 15 7 ...
Problem Given two integer arrays preorder and inorder where preorder is the preorder traversal of a binary tree and inorder is the inorder traversal of the same tree, construct and return the binary tree. Examples Example 1: 3 / \ 9 20 / \ 15 7 ...
Problem Given an integer array, count the number of inversions. What is an inversion? This was taught in Algorithms: Design and Analysis Part I on coursera - how to count inversions. Inversion count is the distance of order of elements in an array from the the sorted order i.e. it indicates how far (or close) the array is from being sorted. If array is already sorted then inversion count is 0. If array is sorted in reverse order that inversion count is the maximum. ...
Find First Unique Character From a Stream of Characters Problem Given a string A denoting a stream of lowercase alphabets. You have to make new string B. B is formed such that we have to find first non-repeating character each time a character is inserted to the stream and append it at the end to B. If no non-repeating character is found then append ’#’ at the end of B. ...
Problem You are given an array of k linked-lists lists, each linked-list is sorted in ascending order. Merge all the linked-lists into one sorted linked-list and return it. Examples 1 -> 10 -> 20 4 -> 11 -> 13 3 -> 8 -> 9 will result in 1 -> 3 -> 4 -> 8 -> 9 -> 10 -> 11 -> 13 -> 20 ...
Problem You are given an n x n 2D matrix representing an image, rotate the image by 90 degrees (clockwise). Another way to ask the same problem Given an image represented by an NxN matrix, where each pixel in the image is 4 bytes, write a method to rotate the image by 90 degrees. Can you do this in place? Examples Example 1: ...
Problem Serialization is the process of converting a data structure or object into a sequence of bits so that it can be stored in a file or memory buffer, or transmitted across a network connection link to be reconstructed later in the same or another computer environment. Design an algorithm to serialize and deserialize a binary tree. There is no restriction on how your serialization/deserialization algorithm should work. You just need to ensure that a binary tree can be serialized to a string and this string can be deserialized to the original tree structure. ...
Problem Given a sequence of words, check whether it forms a valid word square. A sequence of words forms a valid word square if the k_th row and column read the exact same string, where 0 ≤ k < max(numRows, numColumns). Note: Examples Example 1: $$ \begin{bmatrix} \color{red} a & \color{red} b & \color{red} c & \color{red} d \\ \color{red} b & \color{green} n & \color{green} r & \color{green} t \\ \color{red} c & \color{green} r & \color{blue} m & \color{blue} y \\ \color{red} d & \color{green} t & \color{blue} y & \color{violet} e \end{bmatrix} $$ ...
Problem Given a string S, find the length of the longest substring T that contains at most k distinct characters. Examples Example 1: Input: S = "eceba" and k = 3 Output: 4 Explanation: T = "eceb" Example 2: Input: S = "WORLD" and k = 4 Output: 4 Explanation: T = "WORL" or "ORLD" ...
Problem Given an integer array nums where every element appears three times except for one, which appears exactly once. Find the single element and return it. You must implement a solution with a linear runtime complexity and use only constant extra space. Examples Example 1: Input : nums = [1, 2, 4, 3, 3, 2, 2, 3, 1, 1] Output : 4 ...