Two Pointers

ProblemGiven an integer array nums, rotate the array to the right by k steps, where k is non-negative. Example 1: 1234567Input: nums = [1,2,3,4,5,6,7], k = 3Output: [5,6,7,1,2,3,4]Explanation:rotate 1 steps to the right: [7,1,2,3,4,5,6]rotate 2 steps to the right: [6,7,1,2,3,4,5]rotate 3 steps to the right: [5,6,7,1,2,3,4] Example 2: 123456Input: nums = [-1,-100,3,99], k = 2Output: [3,99,-1,-100]Explanation:rotate 1 steps to the right: [99,-1,-100,3]rotate 2 steps to the right: [3,99,-1,-100] ...

ProblemGiven an integer array nums sorted in non-decreasing order, remove some duplicates in-place such that each unique element appears at most twice. The relative order of the elements should be kept the same. Since it is impossible to change the length of the array in some languages, you must instead have the result be placed in the first part of the array nums. More formally, if there are k elements after removing the duplicates, then the first k elements of nums should hold the final result ...

ProblemGiven an integer array nums sorted in non-decreasing order, remove the duplicates in-place such that each unique element appears only once. The relative order of the elements should be kept the same. Then return the number of unique elements in nums. Consider the number of unique elements of nums to be k, to get accepted, you need to do the following things: Change the array nums such that the first k elements of nums contain the unique elements in the order they were present in nums ini ...

ProblemGiven two strings s and t, return true if s is a subsequence of t, or false otherwise. A subsequence of a string is a new string that is formed from the original string by deleting some (can be none) of the characters without disturbing the relative positions of the remaining characters. (i.e., "ace" is a subsequence of "abcde" while "aec" is not). Example 1: 123Input: s = "abc", t = "ahbgdc"Output: true Example 2: 123Input: s = "axc ...

ProblemGiven an integer array nums, move all 0‘s to the end of it while maintaining the relative order of the non-zero elements. Note that you must do this in-place without making a copy of the array. Example 1: 123Input: nums = [0,1,0,3,12]Output: [1,3,12,0,0] Example 2: 123Input: nums = [0]Output: [0] Constraints: 1 <= nums.length <= 10^4 2^31 <= nums[i] <= 2^31 - 1 Follow up: Could you minimize the total number of operations done? Solve123456789101112class Solution: def mov ...

ProblemYou are given two strings word1 and word2. Merge the strings by adding letters in alternating order, starting with word1. If a string is longer than the other, append the additional letters onto the end of the merged string. Return the merged string. Example 1: 1234567Input: word1 = "abc", word2 = "pqr"Output: "apbqcr"Explanation: The merged string will be merged as so:word1: a b cword2: p q rmerged: a p b q c r Example 2: 1234567Input: word1 = & ...

ProblemWrite 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 stay), or it loops endlessly in a cycle which does not include 1. Those numbers for which this process ends in 1 are happy. Return true if n is a happy number, and false if not. Example 1: 12345678Input: n = 19Output: ...

ProblemGiven the head of a linked list, return the list after sorting it in ascending order. Example 1: 123Input: head = [4,2,1,3]Output: [1,2,3,4] Example 2: 123Input: head = [-1,5,3,4,0]Output: [-1,0,3,4,5] Example 3: 12Input: head = []Output: [] Solve1234567891011121314151617181920212223242526272829303132333435363738394041424344class Solution: def sortList(self, head: Optional[ListNode]) -> Optional[ListNode]: # 沒有 或只只有一個 代表已經排好了 if not head or not head.next: ...

#ProblemGiven an integer array nums and an integer val, remove all occurrences of val in nums in-place. The order of the elements may be changed. Then return the number of elements in nums which are not equal to val. Consider the number of elements in nums which are not equal to val be k, to get accepted, you need to do the following things: Change the array nums such that the first k elements of nums contain the elements which are not equal to val. The remaining elements of nums are not import ...

#ProblemYou 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. To accommodate this, nums1 has a length of m + n, where the first m elements denote the elements that should be merged, and the last ...