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LeetCode - Problems - Algorithms - 202. Happy Number LeetCode - The World's Leading Online Programming Learning Platform Level up your coding skills and quickly land a job. This is the best place to expand your knowledge and get prepared for your next interview. leetcode.com My Solution (C#) static public bool IsHappy(int n) { List tracks = new List(); while (!tracks.Contains(n)) { tracks.Add(n)..

LeetCode - Problems - Algorithms - 338. Counting Bits Counting Bits - LeetCode Can you solve this real interview question? Counting Bits - Given an integer n, return an array ans of length n + 1 such that for each i (0

LeetCode - Problems - Algorithms - 125. Same Tree Same Tree - LeetCode Can you solve this real interview question? Same Tree - Given the roots of two binary trees p and q, write a function to check if they are the same or not. Two binary trees are considered the same if they are structurally identical, and the nodes have the leetcode.com My Solution (C#) /** * Definition for a binary tree node. ..

LeetCode - Problems - Algorithms - 100. Valid Palindrome Valid Palindrome - LeetCode Can you solve this real interview question? Valid Palindrome - A phrase is a palindrome if, after converting all uppercase letters into lowercase letters and removing all non-alphanumeric characters, it reads the same forward and backward. Alphanumeric cha leetcode.com My Solution (C#) public class Solution { pu..

LeetCode - Problems - Algorithms - 35. Search Insert Position Problem Description Given a sorted array of distinct integers and a target value, return the index if the target is found. If not, return the index where it would be if it were inserted in order. My Solution (C#) nums에 target을 insert한다고 가정 했을 때, insert 되는 위치를 return하는 문제. nums는 오름차순으로 정렬되어있고, target 또한 오름차순에 맞게 insert 되어야 한다는 조건이 있다. ..

LeetCode - Problems - Algorithms - 28. Implement strStr() Problem Description My Solution (C#) 변수 이름에서 알 수 있듯이, 주어진 string 건초더미에서 string 바늘이 있는지 찾는 문제이다. C#의 IndexOf (C의 경우는 StrStr)를 구현하는 문제다. Description을 끝까지 안읽어서 (끝까지 읽읍시다...) IndexOf를 사용해서 풀었다. (??) // Implementing IndexOf by using IndexOf (???) public class Solution { public int StrStr(string haystack, string needle) { if (string.IsNullOrEmp..

LeetCode - Problems - Algorithms - 27. Remove Element Problem Description My Solution (C#) public class Solution { public int RemoveElement(int[] nums, int val) { if (nums.Length == 0) return 0; int index = 0; foreach (int num in nums) { if (num != val) { nums[index] = num; index++; } } return index; } } 26. Remove Duplicates from Sorted Array와 비슷하게 풀었다. [LeetCode] 26. Remove Duplicates from Sor..

LeetCode - Problems - Algorithms - 26. Remove Duplicates from Sorted Array Problem Description My Solution (C#) public class Solution { public int RemoveDuplicates(int[] nums) { if (nums.Length == 0) return 0; int index = 0; for (int i = 1; i < nums.Length; i++) { if (nums[index] != nums[i]) { nums[++index] = nums[i]; } } return ++index; } } C#의 regular array는 길이를 조절할 수 없는 array이다. 그러다 문제는 array..

LeetCode - Problems - Algorithms - 21. Merge Two Sorted Lists Problem Description Merge two sorted linked lists and return it as a sorted list. The list should be made by splicing together the nodes of the first two lists. My Solution (C#) /** * Definition for singly-linked list. * public class ListNode { * public int val; * public ListNode next; * public ListNode(int val=0, ListNode next=null) ..

LeetCode - Problems - Algorithms - 20. Valid Parentheses Problem Description Given a string s containing just the characters '(', ')', '{', '}', '[' and ']', determine if the input string is valid. An input string is valid if: Open brackets must be closed by the same type of brackets. Open brackets must be closed in the correct order. Example 1: Input: s = "()" Output: true Example 2: Input: s =..