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原创最大子数组 III

给定一个整数数组和一个整数 k，找出 k 个不重叠子数组使得它们的和最大。每个子数组的数字在数组中的位置应该是连续的。返回最大的和。注意事项子数组最少包含一个数样例给出数组 [-1,4,-2,3,-2,3] 以及 k = 2，返回 8public class Solution { /** * @param nums: A list of integers

2017-07-15 17:09:48 580

原创最大子数组 II

给定一个整数数组，找出两个不重叠子数组使得它们的和最大。每个子数组的数字在数组中的位置应该是连续的。返回最大的和。注意事项子数组最少包含一个数样例给出数组 [1, 3, -1, 2, -1, 2] 这两个子数组分别为 [1, 3] 和 [2, -1, 2] 或者 [1, 3, -1, 2] 和 [2]，它们的最大和都是 7 挑战要求时间复杂度为 O(n)publi

2017-07-15 16:51:49 409

The thief has found himself a new place for his thievery again. There is only one entrance to this area, called the “root.” Besides the root, each house has one and only one parent house. After a tour,

2017-05-01 21:04:43 370

原创 324. Wiggle Sort II

Given an unsorted array nums, reorder it such that nums[0] < nums[1] > nums[2] < nums[3]….Example: (1) Given nums = [1, 5, 1, 1, 6, 4], one possible answer is [1, 4, 1, 5, 1, 6]. (2) Given nums = [1

2017-05-01 20:21:34 353

原创 2. Add Two Numbers

You are given two non-empty linked lists representing two non-negative integers. The digits are stored in reverse order and each of their nodes contain a single digit. Add the two numbers and return it

2017-04-29 20:23:21 248

原创 windows10+python3环境搭建

在windows10上搭建好python3之后，用pip安装所需要的包。这里没有使用anaconda，python和pip自行安装。 http://www.lfd.uci.edu/~gohlke/pythonlibs/这里有所需要的pakage。比如下载numpy‑1.12.1+mkl‑cp36‑cp36m‑win_amd64.whl 需要注意cp36是python的版本是python3.

2017-04-29 10:05:09 390

原创 gbdt源码阅读

regressiontree. main函数：训练样本，最大深度，叶子节点最小样本数，特征采样，数据采样。加载训练样本，利用样本构建regressiontree，对训练样本（这里有些问题，实际上应该对样本进行划分）进行预测。 RegressionTree： fit：选取采样特征，递归构建树，选取切分节点（特征）。 split_node: 选取切分点，如果深度达到最大深度或者切分之后左右树没有

2017-04-10 20:44:41 1171

转载 gbdt和随机森林

转载http://blog.youkuaiyun.com/keepreder/article/details/47272779 相同点： 1.都是多棵树组成 2.结果由多棵树决定不同点： 1.随机森林可以是分类树或者回归树，gbdt是回归树。 2.随机森林是投票的方式决定结果，gbdt是各个树的加和作为最终结果。 3.随机森林中的树可以并行构建，gbdt需要串行。 4.随机森林对异常值不敏感，

2017-04-10 15:55:04 627

转载机器学习损失函数

http://www.csuldw.com/2016/03/26/2016-03-26-loss-function/

2017-04-10 15:44:00 328

原创 452. Minimum Number of Arrows to Burst Balloons

There are a number of spherical balloons spread in two-dimensional space. For each balloon, provided input is the start and end coordinates of the horizontal diameter. Since it’s horizontal, y-coordina

2017-04-04 21:14:40 233

原创 213. House Robber II

Note: This is an extension of House Robber.After robbing those houses on that street, the thief has found himself a new place for his thievery so that he will not get too much attention. This time, all

2017-04-04 20:12:40 300

原创 47. Permutations II

Given a collection of numbers that might contain duplicates, return all possible unique permutations.For example, [1,1,2] have the following unique permutations: [ [1,1,2], [1,2,1], [2,1,1]

2017-04-04 19:55:41 367

原创 114. Flatten Binary Tree to Linked List

Given a binary tree, flatten it to a linked list in-place.For example, Given 1 / \ 2 5 / \ \ 3 4 6The flattened tree should look like: 1 \ 2 \ 3

2017-04-04 19:42:24 181

原创 300. Longest Increasing Subsequence

Given an unsorted array of integers, find the length of longest increasing subsequence.For example, Given [10, 9, 2, 5, 3, 7, 101, 18], The longest increasing subsequence is [2, 3, 7, 101], therefore

2017-04-04 19:13:53 199

原创 402. Remove K Digits

Given a non-negative integer num represented as a string, remove k digits from the number so that the new number is the smallest possible.Note:The length of num is less than 10002 and will be ≥ k.The

2017-03-28 20:10:23 347

原创 406. Queue Reconstruction by Height

Suppose you have a random list of people standing in a queue. Each person is described by a pair of integers (h, k), where h is the height of the person and k is the number of people in front of this p

2017-03-28 19:25:58 315

原创 409. Longest Palindrome

Given a string which consists of lowercase or uppercase letters, find the length of the longest palindromes that can be built with those letters.This is case sensitive, for example “Aa” is not consider

2017-03-28 19:25:20 303

原创 414. Third Maximum Number

Given a non-empty array of integers, return the third maximum number in this array. If it does not exist, return the maximum number. The time complexity must be in O(n).Example 1:Input: [3, 2, 1]Output

2017-03-28 15:42:00 261

原创 168. Excel Sheet Column Title

Given a positive integer, return its corresponding column title as appear in an Excel sheet.For example:1 -> A2 -> B3 -> C...26 -> Z27 -> AA28 -> AB public class Solution { public String con

2017-03-26 19:46:25 267

原创 117. Populating Next Right Pointers in Each Node II

Follow up for problem “Populating Next Right Pointers in Each Node”.What if the given tree could be any binary tree? Would your previous solution still work?Note:You may only use constant extra space.

2017-03-26 19:38:53 287

原创 445. Add Two Numbers II

You are given two non-empty linked lists representing two non-negative integers. The most significant digit comes first and each of their nodes contain a single digit. Add the two numbers and return it

2017-03-26 19:17:36 313

原创 73. Set Matrix Zeroes

Given a m x n matrix, if an element is 0, set its entire row and column to 0. Do it in place.click to show follow up.Follow up: Did you use extra space? A straight forward solution using O(mn) space

2017-03-26 18:59:13 381

原创 297. Serialize and Deserialize Binary Tree

Serialization is the process of converting a data structure or object into a sequence of bits so that it can be stored in a file or memory buffer, or transmitted across a network connection link to be

2017-03-26 17:38:14 219

原创 116. Populating Next Right Pointers in Each Node

Given a binary treestruct TreeLinkNode { TreeLinkNode *left; TreeLinkNode *right; TreeLinkNode *next;}Populate each next pointer to point to its next right node. If there is no next right node,

2017-03-26 17:02:56 256

原创 268. Missing Number

Given an array containing n distinct numbers taken from 0, 1, 2, …, n, find the one that is missing from the array.For example, Given nums = [0, 1, 3] return 2.a^b^b = apublic class Solution { pub

2017-03-26 16:03:03 202

原创 218. The Skyline Problem

A city’s skyline is the outer contour of the silhouette formed by all the buildings in that city when viewed from a distance. Now suppose you are given the locations and height of all the buildings as

2017-03-26 15:51:29 375

原创 235. Lowest Common Ancestor of a Binary Search Tree

Given a binary search tree (BST), find the lowest common ancestor (LCA) of two given nodes in the BST.According to the definition of LCA on Wikipedia: “The lowest common ancestor is defined between two

2017-03-26 13:40:51 213

原创 273. Integer to English Words

Convert a non-negative integer to its english words representation. Given input is guaranteed to be less than 231 - 1.For example, 123 -> “One Hundred Twenty Three” 12345 -> “Twelve Thousand Three Hu

2017-03-26 13:26:54 257

原创 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./** * Definition for singly-linked lis

2017-03-26 12:54:42 181

原创 419. Battleships in a Board

Given an 2D board, count how many battleships are in it. The battleships are represented with ‘X’s, empty slots are represented with ‘.’s. You may assume the following rules:You receive a valid board,

2017-03-26 12:25:12 275

原创 xgboost

摘录自知乎。https://www.zhihu.com/question/41354392xgboost和gbdt的区别，为什么快？如何支持并行？ 1.传统gbdt是用CART作为基分类器，xgboost还支持线性分类器。此时xgboost相当于带l1和l2正则化项的逻辑回归（分类问题）或者线性回归（回归问题）。 2.gbdt优化时只用到了一阶求导，xgboost对代价函数进行二阶泰勒展开，同时

2017-03-20 12:18:57 1877

原创删除链表中倒数第n个节点

给定一个链表，删除链表中倒数第n个节点，返回链表的头节点。样例给出链表1->2->3->4->5->null和 n = 2.删除倒数第二个节点之后，这个链表将变成1->2->3->5->null.挑战 O(n)时间复杂度/** * Definition for ListNode. * public class ListNode { * int val; * Lis

2017-03-19 10:19:31 318

原创翻转链表 II

翻转链表中第m个节点到第n个节点的部分样例给出链表1->2->3->4->5->null， m = 2 和n = 4，返回1->4->3->2->5->null挑战在原地一次翻转完成/** * Definition for ListNode * public class ListNode { * int val; * ListNode next; *

2017-03-19 09:56:36 214

原创寻找旋转排序数组中的最小值 II

假设一个旋转排序的数组其起始位置是未知的（比如0 1 2 4 5 6 7 可能变成是4 5 6 7 0 1 2）。你需要找到其中最小的元素。数组中可能存在重复的元素。样例给出[4,4,5,6,7,0,1,2] 返回 0public class Solution { /** * @param num: a rotated sorted array * @retur

2017-03-18 21:13:28 279

原创 153. Find Minimum 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).Find the minimum element.You may assume no duplicate exist

2017-03-18 17:15:48 338

原创机器学习-1

基本问题的经典算法分类：svm、最大熵、adaboost、分类回归树、随机森林回归：分类回归树、随机森林、GBDT 排序：GBRank 聚类：K-Means 结构标注：隐马尔可夫模型、条件随机场。机器学习=表示（算法、特征的表示）+评价（loss+cost评价算法好坏的函数）+优化（寻找使评价函数得分最高的搜索方法比如梯度下降、牛顿法）如何权衡训练误差和预测误差（拟合能力和泛化能力，b

2017-03-17 16:57:14 354

原创广告点击率预估模型

广告点击价值由广告主定价，每次广告投放是投放预期收益最高的广告。点击率预测越准确，越接近最大化收益。挖掘用户日志，根据日志中行为信息给用户打标签。特征提取-单属性特征广告特征：广告商，广告集团，广告品种，广告标题等。用户特征：用户cookie，搜索关键字，tag 上下文特征：页面主题关键字，正文关键字，广告位，browser，page attribute特征提取-交叉特征静态特征-

2017-03-17 12:31:15 2832

原创 151. Reverse Words in a String

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 programmers: Try to solve it in-place in O(1) spa

2017-03-16 23:41:14 477

原创 451. Sort Characters By Frequency

Given a string, sort it in decreasing order based on the frequency of characters.Example 1:Input: “tree”Output: “eert”Explanation: ‘e’ appears twice while ‘r’ and ‘t’ both appear once. So ‘e’ must

2017-03-16 17:16:10 351

原创 397. Integer Replacement

Given a positive integer n and you can do operations as follow: If n is even, replace n with n/2. If n is odd, you can replace n with either n + 1 or n - 1. What is the minimum number of replacement

2017-03-16 16:48:56 244

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