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Here is the link to the problem: Remove duplicates (Linked List). Problem Statement: Given the head of a sorted linked list, delete all duplicates such that each element appears only once. Return the linked list sorted as well. Examples: Example 1: Input: head = [1,1,2] Output: [1,2] Example 2: Input: head = [1,1,2,3,3] Output: [1,2,3] My Solution # Definition for singly-linked list. # class ListNode(object): # def __init__(self, val=0, next=None): # self....

Here is the link to the problem: Valid Sudoku. Problem Statement: Determine if a 9 x 9 Sudoku board is valid. Only the filled cells need to be validated according to the following rules: Each row must contain the digits 1-9 without repetition. Each column must contain the digits 1-9 without repetition. Each of the nine 3 x 3 sub-boxes of the grid must contain the digits 1-9 without repetition....

Here is the link to the problem: Majority Element. Problem Statement: Given an array nums of size n, return the majority element. The majority element is the element that appears more than ⌊n / 2⌋ times. You may assume that the majority element always exists in the array. Examples: Example 1: Input: nums = [3,2,3] Output: 3 Example 2: Input: nums = [2,2,1,1,1,2,2] Output: 2 My Solution class Solution(object): def majorityElement(self, nums): """ :type nums: List[int] :rtype: int """ new_dict = {} for each in nums: if each in new_dict: new_dict[each] += 1 else: new_dict[each] = 1 for each in new_dict: if new_dict[each] > len(nums)/ 2: return each This is nothing, very simple....

Here is the link to the problem: Single Number. Problem Statement: Given a non-empty array of integers nums, every element appears twice except for one. Find that single one. You must implement a solution with a linear runtime complexity and use only constant extra space. Examples: Example 1: Input: nums = [2,2,1] Output: 1 Example 2: Input: nums = [4,1,2,1,2] Output: 4 Example 3: Input: nums = [1] Output: 1...

Here is the link to the problem: Valid Palindrome. Problem Statement: 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 characters include letters and numbers. Given a string s, return true if it is a palindrome, or false otherwise. Examples: Example 1: Input: s = “A man, a plan, a canal: Panama”...

Here is the link to the problem: Merge Sorted Array. Problem Statement: You are given two integer arrays nums1 and nums2, sorted in non-decreasing order, and two integers m and n, representing the number of elements in nums1 and nums2 respectively. Merge nums1 and nums2 into a single array sorted in non-decreasing order. The final sorted array should not be returned by the function, but instead be stored inside the array nums1....

Here is the link to the problem: Climbing Stairs. Problem Statement: You are climbing a staircase. It takes n steps to reach the top. Each time you can either climb 1 or 2 steps. In how many distinct ways can you climb to the top? Examples: Example 1: Input: n = 2 Output: 2 Explanation: There are two ways to climb to the top. 1 step + 1 step 2 steps...

Here is the link to the problem: Square root. Problem Statement: Given a non-negative integer x, return the square root of x rounded down to the nearest integer. The returned integer should be non-negative as well. You must not use any built-in exponent function or operator. For example, do not use pow(x, 0.5) in c++ or x ** 0.5 in python. Examples: Example 1: Input: x = 4 Output: 2...

Here is the link to the problem: Add Binary. Problem Statement: Given two binary strings a and b, return their sum as a binary string. Examples: Example 1: Input: a = “11”, b = “1” Output: “100” Example 2: Input: a = “1010”, b = “1011” Output: “10101” My Solution class Solution(object): def addBinary(self, a, b): """ :type a: str :type b: str :rtype: str """ c = 0 res = "" a_r, b_r = a[::-1], b[::-1] for i in range(max(len(a), len(b))): a_val = a_r[i] if i < len(a) else 0 b_val = b_r[i] if i < len(b) else 0 sum = c + int(a_val) + int(b_val) r = sum % 2 c = sum // 2 res += str(r) if c: return (str(c) + res[::-1]) else: return res[::-1] So even though this is an easy problem, but there are a lot of things to be considered....

Here is the link to the problem: Length of Last word. Problem Statement: Given a string s consisting of words and spaces, return the length of the last word in the string. A word is a maximal substring consisting of non-space characters only. Examples: Example 1: Input: s = “Hello World” Output: 5 Explanation: The last word is “World” with length 5. Example 2: Input: s = " fly me to the moon "...