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Rotate Array Given an array, rotate the array to the right by k steps, where k is non-negative.Example 1:Input: [1,2,3,4,5,6,7] and k = 3 Output: [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:Input: [-1,-100,3,99] and k = 2 Output: [3,99,-1,-100] Explanation: rotate 1 steps to the r.. 더보기
Best Time to Buy and Sell Stock II Say you have an array for which the ith element is the price of a given stock on day i.Design an algorithm to find the maximum profit. You may complete as many transactions as you like (i.e., buy one and sell one share of the stock multiple times).Note: You may not engage in multiple transactions at the same time (i.e., you must sell the stock before you buy again).Example 1:Input: [7,1,5,3,6,4].. 더보기
Reverse Linked List Reverse a singly linked list.Example:Input: 1->2->3->4->5->NULL Output: 5->4->3->2->1->NULL Follow up:A linked list can be reversed either iteratively or recursively. Could you implement both? My Solution:# Definition for singly-linked list. # class ListNode: # def __init__(self, x): # self.val = x # self.next = None class Solution: def reverseList(self, head): """ :type head: ListNode :rtype: L.. 더보기
Remove Nth Node From End of List Given a linked list, remove the n-th node from the end of list and return its head.Example:Given linked list: 1->2->3->4->5, and n = 2. After removing the second node from the end, the linked list becomes 1->2->3->5. Note:Given n will always be valid.Follow up:Could you do this in one pass? My solution:# Definition for singly-linked list. # class ListNode: # def __init__(self, x): # self.val = x.. 더보기
Delete Node in a Linked List Write a function to delete a node (except the tail) in a singly linked list, given only access to that node.Given linked list -- head = [4,5,1,9], which looks like following: 4 -> 5 -> 1 -> 9 Example 1:Input: head = [4,5,1,9], node = 5 Output: [4,1,9] Explanation: You are given the second node with value 5, the linked list should become 4 -> 1 -> 9 after calling your function. Example 2:Input: h.. 더보기
Longest Common Prefix Write a function to find the longest common prefix string amongst an array of strings.If there is no common prefix, return an empty string "".Example 1:Input: ["flower","flow","flight"] Output: "fl" Example 2:Input: ["dog","racecar","car"] Output: "" Explanation: There is no common prefix among the input strings. Note:All given inputs are in lowercase letters a-z. My solution:class Solution: def.. 더보기
Count and Say The count-and-say sequence is the sequence of integers with the first five terms as following:1. 1 2. 11 3. 21 4. 1211 5. 111221 1 is read off as "one 1" or 11. 11 is read off as "two 1s" or 21. 21 is read off as "one 2, then one 1" or 1211.Given an integer n where 1 ≤ n ≤ 30, generate the nth term of the count-and-say sequence.Note: Each term of the sequence of integers will be represented as a.. 더보기
Implement strStr() Implement strStr().Return the index of the first occurrence of needle in haystack, or -1 if needle is not part of haystack.Example 1:Input: haystack = "hello", needle = "ll" Output: 2 Example 2:Input: haystack = "aaaaa", needle = "bba" Output: -1 Clarification:What should we return when needle is an empty string? This is a great question to ask during an interview.For the purpose of this problem.. 더보기
String to Integer (atoi) Implement atoi which converts a string to an integer.The function first discards as many whitespace characters as necessary until the first non-whitespace character is found. Then, starting from this character, takes an optional initial plus or minus sign followed by as many numerical digits as possible, and interprets them as a numerical value.The string can contain additional characters after .. 더보기
Valid Palindrome Given a string, determine if it is a palindrome, considering only alphanumeric characters and ignoring cases.Note: For the purpose of this problem, we define empty string as valid palindrome.Example 1:Input: "A man, a plan, a canal: Panama" Output: true Example 2:Input: "race a car" Output: false My solution:class Solution: def isPalindrome(self, s): """ :type s: str :rtype: bool """ size_s = le.. 더보기

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