leetcode
Leetcode - Reverse Vowels of a String Solution
Given a string s, reverse only all the vowels in the string and return it. The vowels are 'a', 'e', 'i', 'o', and 'u', and they can appear in both cases. Example 1: Input: s = "hello" Output: "
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Leetcode - Count and Say Solution
The count-and-say sequence is a sequence of digit strings defined by the recursive formula: * countAndSay(1) = "1" * countAndSay(n) is the way you would "say" the digit string from countAndSay(n-1), which is then converted into a different digit string. To determine how you "say&
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Leetcode - Reverse String Solution
Write a function that reverses a string. The input string is given as an array of characters s. Example 1: Input: s = ["h","e","l","l","o"] Output: ["o","l","l","e"
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Leetcode - Power of Four Solution
Given an integer n, return true if it is a power of four. Otherwise, return false. An integer n is a power of four, if there exists an integer x such that n == 4x. Example 1: Input: n = 16 Output: true Example 2: Input: n = 5 Output: false Example 3:
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Leetcode - Power of Three Solution
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:
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Leetcode - Bulls and Cows Solution
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
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Leetcode - Word Pattern Solution
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&
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Leetcode - Implement Queue using Stacks Solution
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
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Leetcode - Implement Stack using Queues Solution
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
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Leetcode - Contains Duplicate II Solution
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:
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Leetcode - Minimum Size Subarray Sum Solution
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,
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Leetcode - Happy Number Solution
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