2018 年 2月随笔档案 - Beserious

leetcode 404. Sum of Left Leaves

摘要：Find the sum of all left leaves in a given binary tree. 思路：在递归的时候访问左右节点记录一下，比如做节点标记1，右节点标2，那么当遍历到叶子节点的时候，我们只加标记为1的叶子节点的值。阅读全文

posted @ 2018-02-28 19:39 Beserious 阅读(51) 评论(0) 推荐(0) 编辑

leetcode 263. Ugly Number

摘要：Write a program to check whether a given number is an ugly number. Ugly numbers are positive numbers whose prime factors only include 2, 3, 5. For exa 阅读全文

posted @ 2018-02-28 19:34 Beserious 阅读(83) 评论(0) 推荐(0) 编辑

leetcode 278. First Bad Version

摘要：You are a product manager and currently leading a team to develop a new product. Unfortunately, the latest version of your product fails the quality c 阅读全文

posted @ 2018-02-28 19:33 Beserious 阅读(91) 评论(0) 推荐(0) 编辑

leetcode 303. Range Sum Query - Immutable

摘要：Given an integer array nums, find the sum of the elements between indices i and j (i ≤ j), inclusive. 前缀和思想。如果修改的次数比较多，那么就可以用线段树了, class NumArray { pu 阅读全文

posted @ 2018-02-28 19:29 Beserious 阅读(84) 评论(0) 推荐(0) 编辑

leetcode 326. Power of Three

摘要：Given an integer, write a function to determine if it is a power of three. 判断一个数，是不是3的n次幂。直接换底公式求解阅读全文

posted @ 2018-02-28 19:22 Beserious 阅读(86) 评论(0) 推荐(0) 编辑

leetcode 350. Intersection of Two Arrays II

摘要：Given two arrays, write a function to compute their intersection. Example: Given nums1 = [1, 2, 2, 1], nums2 = [2, 2], return [2, 2]. Note: Each eleme 阅读全文

posted @ 2018-02-28 19:07 Beserious 阅读(97) 评论(0) 推荐(0) 编辑

leetcode 371. Sum of Two Integers

摘要：Calculate the sum of two integers a and b, but you are not allowed to use the operator + and . Example: Given a = 1 and b = 2, return 3. 不用加减法进行求和运算。阅读全文

posted @ 2018-02-28 19:03 Beserious 阅读(104) 评论(0) 推荐(0) 编辑

leetcode 237. Delete Node in a Linked List

摘要：Write a function to delete a node (except the tail) in a singly linked list, given only access to that node. Supposed the linked list is 1 2 3 4 and y 阅读全文

posted @ 2018-02-28 18:25 Beserious 阅读(82) 评论(0) 推荐(0) 编辑

leetcode 367. Valid Perfect Square

摘要：Given a positive integer num, write a function which returns True if num is a perfect square else False. Note: Do not use any built in library functio 阅读全文

posted @ 2018-02-28 18:23 Beserious 阅读(123) 评论(0) 推荐(0) 编辑

leetcode 234. Palindrome Linked List

摘要：Given a singly linked list, determine if it is a palindrome. Follow up: Could you do it in O(n) time and O(1) space? 判断一个链表是不是回文的。思路：遍历节点得到总数tot，然后反转阅读全文

posted @ 2018-02-28 18:21 Beserious 阅读(105) 评论(0) 推荐(0) 编辑

leetcode 232. Implement Queue using Stacks

摘要：Implement the following operations of a queue using stacks. push(x) Push element x to the back of queue. pop() Removes the element from in front of qu 阅读全文

posted @ 2018-02-28 18:16 Beserious 阅读(131) 评论(0) 推荐(0) 编辑

leetcode 225. Implement Stack using Queues

摘要：Implement the following operations of a stack using queues. push(x) Push element x onto stack. pop() Removes the element on top of the stack. top() Ge 阅读全文

posted @ 2018-02-28 18:14 Beserious 阅读(129) 评论(0) 推荐(0) 编辑

leetcode 206. Reverse Linked List

摘要：Reverse a singly linked list. 思路：递归，每次保存一下上一个节点用来构造反转后的链表。非递归，需要多记录两个值. 阅读全文

posted @ 2018-02-28 18:09 Beserious 阅读(90) 评论(0) 推荐(0) 编辑

leetcode 205. Isomorphic Strings

摘要：Given two strings s and t, determine if they are isomorphic. Two strings are isomorphic if the characters in s can be replaced to get t. All occurrenc 阅读全文

posted @ 2018-02-28 16:15 Beserious 阅读(104) 评论(0) 推荐(0) 编辑

leetcode 203. Remove Linked List Elements

摘要：Remove all elements from a linked list of integers that have value val. 思路：声明两指针，类似快慢指针，快指针遇到val时跳过，直到值不是val这时修改慢指针的next为快指针，慢指针移到快指针这个位置。阅读全文

posted @ 2018-02-28 16:00 Beserious 阅读(81) 评论(0) 推荐(0) 编辑

leetcode 198. House Robber

摘要：You are a professional robber planning to rob houses along a street. Each house has a certain amount of money stashed, the only constraint stopping yo 阅读全文

posted @ 2018-02-28 15:15 Beserious 阅读(105) 评论(0) 推荐(0) 编辑

leetcode 190. Reverse Bits

摘要：Reverse bits of a given 32 bits unsigned integer. For example, given input 43261596 (represented in binary as 00000010100101000001111010011100), retur 阅读全文

posted @ 2018-02-28 15:10 Beserious 阅读(80) 评论(0) 推荐(0) 编辑

leetcode leetcode 783. Minimum Distance Between BST Nodes

摘要：Given a Binary Search Tree (BST) with the root node root, return the minimum difference between the values of any two different nodes in the tree. Not 阅读全文

posted @ 2018-02-28 15:08 Beserious 阅读(296) 评论(0) 推荐(0) 编辑

leetcode 202. Happy Number

摘要：Write an algorithm to determine if a number is "happy". A happy number is a number defined by the following process: Starting with any positive intege 阅读全文

posted @ 2018-02-28 15:07 Beserious 阅读(109) 评论(0) 推荐(0) 编辑

leetcode 389. Find the Difference

摘要：Given two strings s and t which consist of only lowercase letters. String t is generated by random shuffling string s and then add one more letter at 阅读全文

posted @ 2018-02-28 15:03 Beserious 阅读(114) 评论(0) 推荐(0) 编辑

leetcode 594. Longest Harmonious Subsequence

摘要：We define a harmonious array is an array where the difference between its maximum value and its minimum value is exactly 1. Now, given an integer arra 阅读全文

posted @ 2018-02-28 14:54 Beserious 阅读(105) 评论(0) 推荐(0) 编辑

leetcode 151. Reverse Words in a String

摘要：Given an input string, reverse the string word by word. For example, Given s = "the sky is blue", return "blue is sky the". Update (2015 02 12): For C 阅读全文

posted @ 2018-02-28 14:49 Beserious 阅读(83) 评论(0) 推荐(0) 编辑

leetcode 747. Largest Number At Least Twice of Others

摘要：In a given integer array nums, there is always exactly one largest element. Find whether the largest element in the array is at least twice as much as 阅读全文

posted @ 2018-02-28 13:26 Beserious 阅读(108) 评论(0) 推荐(0) 编辑

leetcode 767. Reorganize String

摘要：Given a string S, check if the letters can be rearranged so that two characters that are adjacent to each other are not the same. If possible, output 阅读全文

posted @ 2018-02-28 13:21 Beserious 阅读(292) 评论(0) 推荐(0) 编辑

leetcode 789. Escape The Ghosts

摘要：You are playing a simplified Pacman game. You start at the point (0, 0), and your destination is (target[0], target[1]). There are several ghosts on t 阅读全文

posted @ 2018-02-25 19:07 Beserious 阅读(403) 评论(0) 推荐(0) 编辑

leetcode 791. Custom Sort String

摘要：S and T are strings composed of lowercase letters. In S, no letter occurs more than once. S was sorted in some custom order previously. We want to per 阅读全文

posted @ 2018-02-25 19:06 Beserious 阅读(370) 评论(0) 推荐(0) 编辑

leetcode 788. Rotated Digits

摘要：X is a good number if after rotating each digit individually by 180 degrees, we get a valid number that is different from X. A number is valid if each 阅读全文

posted @ 2018-02-25 19:05 Beserious 阅读(503) 评论(0) 推荐(0) 编辑

leetcode 790. Domino and Tromino Tiling

摘要：We have two types of tiles: a 2x1 domino shape, and an "L" tromino shape. These shapes may be rotated. XX 阅读全文

posted @ 2018-02-25 19:03 Beserious 阅读(809) 评论(0) 推荐(0) 编辑

leetcode 784. Letter Case Permutation

摘要：Given a string S, we can transform every letter individually to be lowercase or uppercase to create another string. Return a list of all possible stri 阅读全文

posted @ 2018-02-23 15:26 Beserious 阅读(328) 评论(0) 推荐(0) 编辑

leetcode 720. Longest Word in Dictionary

摘要：Given a list of strings words representing an English Dictionary, find the longest word in words that can be built one character at a time by other wo 阅读全文

posted @ 2018-02-23 15:01 Beserious 阅读(135) 评论(0) 推荐(0) 编辑