zyp7355-优快云博客

原创 leetcode #92Reverse Linked List II

Reverse a linked list from position m to n. Do it in one-pass. Note: 1 ≤ m ≤ n ≤ length of list. Example: Input: 1->2->3->4->5->NULL, m = 2, n = 4 Output: 1->4->3->2->5->...

2020-04-17 05:56:59 203 1

原创 leetcode #88merge sort array

Given two sorted integer arrays nums1 and nums2, merge nums2 into nums1 as one sorted array. Note: The number of elements initialized in nums1 and nums2 are m and n respectively. You may assume that n...

2020-04-16 14:17:17 156

原创 leetcode#74Search a 2D Matrix

Write an efficient algorithm that searches for a value in an m x n matrix. This matrix has the following properties: Integers in each row are sorted from left to right. The first integer of each row i...

2020-04-14 11:03:09 174

原创 leetcode#70 climbing stair

ou are climbing a stair case. It takes n steps to reach to the top. Each time you can either climb 1 or 2 steps. In how many distinct ways can you climb to the top? Note: Given n will be a positive in...

2020-04-14 05:49:21 144

原创 leetcode#69 sqrt()

利用二分搜索，从1到x搜索 if(x<=1) { return x; } int begin = 1; int end = x; int middle = 0; while(begin<=end) { middle = begin + (end - begin)/2; //不要写成middle*m...

2020-04-14 05:36:30 122

原创 leetcode #58 length of last word

Length of Last Word Easy 558 2203 Add to List Share Given a string s consists of upper/lower-case alphabets and empty space characters ’ ', return the length of last word (last word means the last a...

2020-04-08 04:07:10 116

原创 leetcode 56 merge intervals

Merge Intervals Medium 3494 257 Add to List Share Given a collection of intervals, merge all overlapping intervals. Example 1: Input: [[1,3],[2,6],[8,10],[15,18]] Output: [[1,6],[8,10],[15,18]] Expl...

2020-04-08 03:38:05 157

原创 leetcode # 49 group anagrams

Given an array of strings, group anagrams together. Example: Input: [“eat”, “tea”, “tan”, “ate”, “nat”, “bat”], Output: [ [“ate”,“eat”,“tea”], [“nat”,“tan”], [“bat”] ] Note: All inputs will be in lowe...

2020-04-04 02:54:22 138

原创 leetcode#49. Group Anagrams

Given an array of strings, group anagrams together. Example: Input: [“eat”, “tea”, “tan”, “ate”, “nat”, “bat”], Output: [ [“ate”,“eat”,“tea”], [“nat”,“tan”], [“bat”] ] Note: All inputs will be in lowe...

2020-04-04 02:16:56 119

原创 leetcode 48 # rotate image

You are given an n x n 2D matrix representing an image. Rotate the image by 90 degrees (clockwise). Note: You have to rotate the image in-place, which means you have to modify the input 2D matrix dire...

2020-04-03 04:39:10 111

原创 leetcode #43 Multiply Strings

Given two non-negative integers num1 and num2 represented as strings, return the product of num1 and num2, also represented as a string. Example 1: Input: num1 = “2”, num2 = “3” Output: “6” Example 2:...

2020-04-03 03:20:35 131

原创 leetcode回溯法总结

第二遍做leetcode 中的回溯法，发现不光没有更好的理解，甚至遗忘了很多。所以今天觉得做一篇有关回溯法的总结首先，回溯法的基本思想：从一条路往前走，能进则进，不能进则退回，换一条路再试回溯法的基本定义和概念首先要明确下面三个概念 1约束函数：约束函数是根据题意定出，通过描述合法解的一般特征用于去除不合法的解，从而避免继续搜索出这个不合法解的剩余部分 2状态空间树状态空间树是一个对...

2020-04-02 04:14:49 217

原创 leetcode#33. Search in Rotated Sorted Array

Suppose an array sorted in ascending order is rotated at some pivot unknown to you beforehand. (i.e., [0,1,2,4,5,6,7] might become [4,5,6,7,0,1,2]). You are given a target value to search. If found in...

2020-03-26 06:50:04 107

原创 leetcode #26 Remove Duplicates from Sorted Array

Given a sorted array nums, remove the duplicates in-place such that each element appear only once and return the new length. Do not allocate extra space for another array, you must do this by modifyin...

2020-03-24 06:47:52 137

原创 Leetcode #24. Swap Nodes in Pairs java

Given a linked list, swap every two adjacent nodes and return its head. You may not modify the values in the list’s nodes, only nodes itself may be changed. Example: Given 1->2->3->4, you sho...

2020-03-24 06:23:59 98

原创 leetcode #17. Letter Combinations of a Phone Number

Given a string containing digits from 2-9 inclusive, return all possible letter combinations that the number could represent. A mapping of digit to letters (just like on the telephone buttons) is give...

2020-03-20 09:01:55 128

原创 leetcode#14. 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...

2020-03-18 13:02:06 142

原创 leetcode#150. Evaluate Reverse Polish Notation

Evaluate the value of an arithmetic expression in Reverse Polish Notation. Valid operators are +, -, *, /. Each operand may be an integer or another expression. Note: Division between two integers sho...

2020-03-07 10:48:49 92

原创 #148. Sort List

Sort a linked list in O(n log n) time using constant space complexity. Example 1: Input: 4->2->1->3 Output: 1->2->3->4 Example 2: Input: -1->5->3->4->0 Output: -1->0-&...

2020-03-07 05:57:07 98

原创 leetcode #147. Insertion Sort List

Sort a linked list using insertion sort. A graphical example of insertion sort. The partial sorted list (black) initially contains only the first element in the list. With each iteration one element (...

2020-03-06 14:49:19 137

原创 leetcode #143. Reorder List

Given a singly linked list L: L0→L1→…→Ln-1→Ln, reorder it to: L0→Ln→L1→Ln-1→L2→Ln-2→… You may not modify the values in the list’s nodes, only nodes itself may be changed. Example 1: Given 1->2->...

2020-03-06 04:02:44 117

原创 leetcode#142. Linked List Cycle II

Given a linked list, return the node where the cycle begins. If there is no cycle, return null. To represent a cycle in the given linked list, we use an integer pos which represents the position (0-in...

2020-03-05 08:08:23 148

原创 leetcode #141. Linked List Cycle

Given a linked list, determine if it has a cycle in it. To represent a cycle in the given linked list, we use an integer pos which represents the position (0-indexed) in the linked list where tail con...

2020-03-05 06:52:13 132

原创 leetcode #138. Copy List with Random Pointer

A linked list is given such that each node contains an additional random pointer which could point to any node in the list or null. Return a deep copy of the list. The Linked List is represented in th...

2020-03-05 04:14:26 190

原创 leetcode #136. Single Number

Given a non-empty array of integers, every element appears twice except for one. Find that single one. Note: Your algorithm should have a linear runtime complexity. Could you implement it without usin...

2020-03-04 13:55:31 114

原创 leetcode #134. Gas Station

There are N gas stations along a circular route, where the amount of gas at station i is gas[i]. You have a car with an unlimited gas tank and it costs cost[i] of gas to travel from station i to its n...

2020-03-04 12:31:50 216

原创 leetcode #131 Palindrome Partitioning

Given a string s, partition s such that every substring of the partition is a palindrome. Return all possible palindrome partitioning of s. Example: Input: “aab” Output: [ [“aa”,“b”], [“a”,“a”,“b”] ] ...

2020-03-04 12:01:58 123

原创 leetcode #122. 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...

2020-03-04 04:30:15 119

原创 letcode#119. Pascal's Triangle II

Given a non-negative index k where k ≤ 33, return the kth index row of the Pascal’s triangle. Note that the row index starts from 0. In Pascal’s triangle, each number is the sum of the two numbers dir...

2020-03-03 07:36:29 103

原创 leetcode#116 Populating Next Right Pointers in Each Node

You are given a perfect binary tree where all leaves are on the same level, and every parent has two children. The binary tree has the following definition: struct Node { int val; Node *left; Node *ri...

2020-02-29 05:25:42 111

原创 leetcode #114. Flatten Binary Tree to Linked List

Given a binary tree, flatten it to a linked list in-place. For example, given the following tree: 1 / 2 5 / \ 3 4 6 The flattened tree should look like: 1 2 3 4 5 6 知识点 stack 先进先出 pop ...

2020-02-28 13:49:42 115

原创 leetcode#113. Path Sum II

Given a binary tree and a sum, find all root-to-leaf paths where each path’s sum equals the given sum. Note: A leaf is a node with no children. Example: Given the below binary tree and sum = 22, 5 ...

2020-02-28 04:19:27 129

原创 leetcode #111. Minimum Depth of Binary Tree

Given a binary tree, find its minimum depth. The minimum depth is the number of nodes along the shortest path from the root node down to the nearest leaf node. Note: A leaf is a node with no children....

2020-02-27 07:45:25 125

原创 leetcode#110. Balanced Binary Tree

Given a binary tree, determine if it is height-balanced. For this problem, a height-balanced binary tree is defined as: a binary tree in which the left and right subtrees of every node differ in heigh...

2020-02-27 06:48:14 121

原创 leetcode#109. Convert Sorted List to Binary Search Tree

Given a singly linked list where elements are sorted in ascending order, convert it to a height balanced BST. For this problem, a height-balanced binary tree is defined as a binary tree in which the d...

2020-02-26 13:47:17 111

原创 leetcode#108. Convert Sorted Array to Binary Search Tree

二分查找中的问题循环条件为什么不是 (l<r) 第一，如果数组长度为1的话，不管查找什么都会恒定的返回-1，这显然是错的。第二，当l + 1 = r的时候，mid=l，如果此时A[mid]小于target执行l=mid+1=r，再次循环时候while条件不满足，将退出循环，但是A[right]可能==target。考虑[3,5] k=5的情况，这时候会返 nick大神讲解看了视频发现了...

2020-02-26 07:45:08 129

原创 leetcode#102Binary Tree Level Order Traversal

Given a binary tree, return the level order traversal of its nodes’ values. (ie, from left to right, level by level). For example: Given binary tree [3,9,20,null,null,15,7], 3 / 9 20 / 15 7 retu...

2020-02-26 06:34:22 103

原创 leetcode #107. Binary Tree Level Order Traversal II

Binary Tree Level Order Traversal II Easy 1039 186 Add to List Share Given a binary tree, return the bottom-up level order traversal of its nodes’ values. (ie, from left to right, level by level fro...

2020-02-26 06:33:46 149

原创 leetcode#105 Construct Binary Tree from Preorder and Inorder Traversal

Given preorder and inorder traversal of a tree, construct the binary tree. Note: You may assume that duplicates do not exist in the tree. For example, given preorder = [3,9,20,15,7] inorder = [9,3,15,...

2020-02-26 06:00:38 105

原创 leetcode #79. Word Search

Given a 2D board and a word, find if the word exists in the grid. The word can be constructed from letters of sequentially adjacent cell, where “adjacent” cells are those horizontally or vertically ne...

2020-02-26 05:25:46 121

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