Problem Given the heads of two singly linked-lists headA and headB, return the node at which the two lists intersect. If the two linked lists have no intersection at all, return null. Intersection point means end of one linked list is linked with some node in another linked list and it forms a Y shape. Input: Two Linked List Output: Intersection Node or point, find Intersection Point in Two Linked List ...
Problem The n-queens puzzle is the problem of placing n queens on an n x n chessboard such that no two queens attack each other. Given an integer n, return all distinct solutions to the n-queens puzzle. You may return the answer in any order. Each solution contains a distinct board configuration of the n-queens’ placement, where 'Q' and '.' both indicate a queen and an empty space, respectively. ...
Problem Given an array of integers nums containing n + 1 integers where each integer is in the range [1, n] inclusive. There is only one repeated number in nums, return this repeated number. You must solve the problem without modifying the array nums and uses only constant extra space. OR You are given an array of length n + 1 whose elements belong to the set {1, 2, ..., n}. By the pigeonhole principle, there must be a duplicate. Find it in linear time and space. ...
Problem An XOR linked list is a more memory efficient doubly linked list. Instead of each node holding next and prev fields, it holds a field named both, which is an XOR of the next node and the previous node. Implement an XOR linked list; it has an add(element) which adds the element to the end, and a get(index) which returns the node at index. If using a language that has no pointers (such as Python), you can assume you have access to get_pointer and dereference_pointer functions that converts between nodes and memory addresses. ...
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 Given a set of distinct integers/characters, S, return all possible subsets. OR Given an integer array nums of unique elements, return all possible subsets (the power set). Examples If we’re given a set of integers such that S = {1, 2, 3}, how can we find all the subsets of that set? For example, given S, the set of all subsets i.e. P(S) we get are {}, {1}, {2}, {3}, {1, 2}, {1, 3}, {2, 3}, and {1, 2, 3}. Here is {} is empty set denoted by Φ. ...
Problem Given an integer array nums, return an array answer such that answer[i] is equal to the product of all the elements of nums except nums[i]. Examples Example 1: Input: nums = [1,2,3,4] Output: [24,12,8,6] Example 2: Input: nums = [-1,1,0,-3,3] Output: [0,0,9,0,0] Constraints 2 <= nums.length <= 105 -30 <= nums[i] <= 30 The product of any prefix or suffix of nums is guaranteed to fit in a 32-bit integer. Follow up Can you solve the problem in O(1) extra space complexity? (The output array does not count as extra space for space complexity analysis.) ...
Problem Implement a first in first out (FIFO) queue using only two stacks. The implemented queue should support all the functions of a normal queue (push, peek, pop, and empty). Implement the MyQueue class: void push(int x) Pushes element x to the back of the queue. int pop() Removes the element from the front of the queue and returns it. int peek() Returns the element at the front of the queue. boolean empty() Returns true if the queue is empty, false otherwise. Notes: ...
Problem Given an m x n 2D binary grid grid which represents a map of '1's (land) and '0's (water), return the number of islands. An island is surrounded by water and is formed by connecting adjacent lands horizontally or vertically. You may assume all four edges of the grid are all surrounded by water. Examples Example 1: Input: grid = [ ["1","1","1","1","0"], ["1","1","0","1","0"], ["1","1","0","0","0"], ["0","0","0","0","0"] ] Output: 1 ...
Problem A message containing letters from A-Z can be encoded into numbers using the following mapping: 'A' -> 1 'B' -> 2 ... 'Z' -> 26 To decode an encoded message, all the digits must be grouped then mapped back into letters using the reverse of the mapping above (there may be multiple ways). For example, "11106" can be mapped into: ...