leetcode Valid Perfect Square
Given a positive integer num, write a function which returns True if num is a perfect square else False.
Note: Do not use any built-in library function such as
12 Input: 16Returns: True
12 Input: 14Returns: False
leetcode Water and Jug Problem
You are given two jugs with capacities x and y litres. There is an infinite amount of water supply available. You need to determine whether it is possible to measure exactly z litres using these two jugs.
- Fill any of the jugs completely.
- Empty any of the jugs.
- Pour water from one jug into another till the other jug is completely full or the first jug itself is empty.
12 Input: x = 2, y = 6, z = 4Output: True
12 Input: x = 2, y = 6, z = 5Output: False
leetcode Max Sum of Rectangle No Larger Than K
Given a non-empty 2D matrix matrix and an integer k, find the max sum of a rectangle in the matrix such that its sum is no larger than k.
12345 Given matrix = [[1, 0, 1],[0, -2, 3]]k = 2
The answer is
2. Because the sum of rectangle
[[0, 1], [-2, 3]]is 2 and 2 is the max number no larger than k (k = 2).
- The rectangle inside the matrix must have an area > 0.
- What if the number of rows is much larger than the number of columns?
leetcode Count Numbers with Unique Digits
Given a non-negative integer n, count all numbers with unique digits, x, where 0 ≤ x < 10n.
Given n = 2, return 91. (The answer should be the total numbers in the range of 0 ≤ x < 100, excluding
leetcode Design Twitter
Design a simplified version of Twitter where users can post tweets, follow/unfollow another user and is able to see the 10 most recent tweets in the user’s news feed. Your design should support the following methods:
- postTweet(userId, tweetId): Compose a new tweet.
- getNewsFeed(userId): Retrieve the 10 most recent tweet ids in the user’s news feed. Each item in the news feed must be posted by users who the user followed or by the user herself. Tweets must be ordered from most recent to least recent.
- follow(followerId, followeeId): Follower follows a followee.
- unfollow(followerId, followeeId): Follower unfollows a followee.
123456789101112131415161718192021222324 Twitter twitter = new Twitter();// User 1 posts a new tweet (id = 5).twitter.postTweet(1, 5);// User 1's news feed should return a list with 1 tweet id -> .twitter.getNewsFeed(1);// User 1 follows user 2.twitter.follow(1, 2);// User 2 posts a new tweet (id = 6).twitter.postTweet(2, 6);// User 1's news feed should return a list with 2 tweet ids -> [6, 5].// Tweet id 6 should precede tweet id 5 because it is posted after tweet id 5.twitter.getNewsFeed(1);// User 1 unfollows user 2.twitter.unfollow(1, 2);// User 1's news feed should return a list with 1 tweet id -> ,// since user 1 is no longer following user 2.twitter.getNewsFeed(1);
leetcode 169. Majority Element
Given an array of size n, find the majority element. The majority element is the element that appears more than⌊ n/2 ⌋ times.
You may assume that the array is non-empty and the majority element always exist in the array.
leetcode Russian Doll Envelopes
You have a number of envelopes with widths and heights given as a pair of integers
(w, h). One envelope can fit into another if and only if both the width and height of one envelope is greater than the width and height of the other envelope.
What is the maximum number of envelopes can you Russian doll? (put one inside other)
Given envelopes =
[[5,4],[6,4],[6,7],[2,3]], the maximum number of envelopes you can Russian doll is
3([2,3] => [5,4] => [6,7]).
leetcode Intersection of Two Arrays
Given two arrays, write a function to compute their intersection.
Given nums1 =
[1, 2, 2, 1], nums2 =
[2, 2], return
- Each element in the result must be unique.
- The result can be in any order.
leetcode Top K Frequent Elements
Given a non-empty array of integers, return the k most frequent elements.
[1,1,1,2,2,3]and k = 2, return
- You may assume k is always valid, 1 ≤ k ≤ number of unique elements.
- Your algorithm’s time complexity must be better than O(n log n), where n is the array’s size.
leetcode Reverse String
Write a function that takes a string as input and returns the string reversed.
Given s = “hello”, return “olleh”.