leetcode
Given an integer n, return true if it is a power of three. Otherwise, return false. An integer n is a power of three, if there exists an integer x such that n == 3x. Example 1: Input: n = 27 Output: true Example 2: Input: n = 0 Output: false Example 3:
leetcode
You are playing the Bulls and Cows game with your friend. You write down a secret number and ask your friend to guess what the number is. When your friend makes a guess, you provide a hint with the following info: * The number of "bulls", which are digits
leetcode
Given a pattern and a string s, find if s follows the same pattern. Here follow means a full match, such that there is a bijection between a letter in pattern and a non-empty word in s. Example 1: Input: pattern = "abba", s = "dog cat cat dog&
leetcode
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
leetcode
Implement a last in first out (LIFO) stack using only two queues. The implemented stack should support all the functions of a normal queue (push, top, pop, and empty). Implement the MyStack class: * void push(int x) Pushes element x to the top of the stack. * int pop() Removes the
leetcode
Given an integer array nums and an integer k, return true if there are two distinct indices i and j in the array such that nums[i] == nums[j] and abs(i - j) <= k. Example 1: Input: nums = [1,2,3,1], k = 3 Output: true Example 2:
leetcode
Given an array of positive integers nums and a positive integer target, return the minimal length of a contiguous subarray [numsl, numsl+1, ..., numsr-1, numsr] of which the sum is greater than or equal to target. If there is no such subarray, return 0 instead. Example 1: Input: target = 7,
leetcode
Write an algorithm to determine if a number n is happy. A happy number is a number defined by the following process: * Starting with any positive integer, replace the number by the sum of the squares of its digits. * Repeat the process until the number equals 1 (where it will
leetcode
Design a stack that supports push, pop, top, and retrieving the minimum element in constant time. Implement the MinStack class: * MinStack() initializes the stack object. * void push(val) pushes the element val onto the stack. * void pop() removes the element on the top of the stack. * int top() gets the
leetcode
Given a non-empty array of integers nums, every element appears twice except for one. Find that single one. Follow up: Could you implement a solution with a linear runtime complexity and without using extra memory? Example 1: Input: nums = [2,2,1] Output: 1 Example 2: Input: nums = [4,1,
leetcode
You are given an array prices where prices[i] is the price of a given stock on the ith day. Find the maximum profit you can achieve. You may complete as many transactions as you like (i.e., buy one and sell one share of the stock multiple times). Note:
leetcode
You are given an array prices where prices[i] is the price of a given stock on the ith day. You want to maximize your profit by choosing a single day to buy one stock and choosing a different day in the future to sell that stock. Return the maximum