Eathen_Zheng-CSDN博客

原创我的个人网站

我的个人网站：Eathen’s Blog 我的 CSDN：Eathen 的练级之路我的 Github：Eathen’s Github 我的知乎：Eathen一名学习机器学习/深度学习的研究生，希望能与志同道合的朋友相互交流，共同进步。...

2018-04-03 20:10:52 198

原创《机器学习基石》笔记系列

前言“机器学习基石”是 Coursera 上一门关于机器学习的课程，由国立台湾大学的老师林轩田讲授。该课程一共有16节课，主要介绍了机器学习领域的基础理论知识。授课大纲课程的大纲如下，以下的每个小项目对应到约一小时的课程：When Can Machines Learn? [何时可以使用机器学习] – The Learning Problem [机器学习问题] – Lear...

2018-03-24 16:57:42 353

原创《机器学习基石》9-Linear Regression

这一节主要介绍线性回归算法。Linear Regression Problem对于输出空间 Y=RY=R\mathcal{Y} = \Bbb{R} 的一类问题，一个比较简单的想法就是：将 Linear Classification 的决策函数中的 sign 函数去掉，使用各种特征的加权结果来表示 yyy y≈∑i=0dwixi=wTxy≈∑i=0dwixi=wTxy \approx ...

2018-04-03 20:18:51 263

原创《机器学习基石》8-Noise and Error

这一节主要讨论在有噪声的情况下，VC维理论是否仍适用。Noise and Probabilistic Target回顾之前提到的机器学习的流程图，学习的目的，就是找到一个函数 ggg，使得它与目标函数 fff 差不多。然而在现实生活中，往往伴随着噪声：这些噪声的类别是多种多样的noise in yyy：如标签标错了noise in xxx：如原本的数据就存在噪声...

2018-04-03 20:16:24 267

原创《机器学习基石》6-Theory of Generalization

Restriction of Break Point上次我们说到，需要探究 “break point” kkk 与 mH(N)mH(N)m_\mathcal{H}(N) 之间的关系。回顾一下，mH(N)mH(N)m_\mathcal{H}(N) 表示假设空间在 NNN 个样本点上能产生的最大二分数量，kkk 表示不能满足完全分类情形的样本点数。让我们来探讨一下，当 kkk 确定时，mH(N...

2018-04-03 20:14:22 342

原创《机器学习基石》5-Training versus Testing

接着上一篇所讨论的问题，继续讨论。Recap and Preview回顾一下机器学习的流程图：机器学习可以理解为寻找到 ggg，使得 g≈fg≈fg \approx f，也就是 Eout(g)≈0Eout(g)≈0E_{out}(g) \approx 0 的过程。为了完成这件事情，有两个关键的步骤：保证 Eout(g)≈Ein(g)Eout(g)≈Ein(g)E_{o...

2018-03-24 17:37:02 236

原创《机器学习基石》4-Feasibility of Learning

在这篇文章中，我们主要探讨，机器到底能不能进行学习这个问题。Learning is Impossible?从前面的文章中，我们已经知道，机器学习的过程，就是通过现有的训练集 DDD 学习，得到预测函数 hhh，并且使得它接近于目标函数 fff。我们必须思考的问题是：这种预测是可能的么？也就是说，机器能通过学习得到 hhh，使得 h≈fh≈fh \approx f 吗？N...

2018-03-24 17:36:38 285

原创《机器学习基石》3-Types of Learning

这节课主要介绍机器学习问题的一些分类。Learning with Different Output Space YY\mathcal{Y}按照数据的输出，可以把 ML 分为以下几类：二类别分类问题：Y∈{0,1}Y∈{0,1}\mathcal{Y} \in \{0, 1\}多类别分类问题：Y∈{0,1,⋯,K}Y∈{0,1,⋯,K}\mathcal{Y} \in \{0, 1,...

2018-03-24 17:35:40 194

原创《机器学习基石》2-Learning to Answer Yes/No

这节课主要介绍感知器算法（Perceptron Learning Algorithm）。Perceptron Hypothesis Set对于一个线性可分的二分类问题，我们可以采用感知器（Perceptron）这种假设集。采用这种假设集进行分类的思想是这样的：我们假设样本的类别是由样本每一个特征 xixi\textbf{x}_i 共同决定，其中不同的特征的重要程度不一样。于是...

2018-03-24 17:32:27 282

原创《机器学习基石》1-The Learning Problem

IntrodctionWhat is Machine Learning机器学习：计算机通过数据和计算获得一定技巧的过程。技巧：指的是在某些事情上表现更加出色，比如预测、识别等等。Why using Machine Learning一些数据或者信息，人来无法获取，可能是一些人无法识别的事物，或是数据信息量特别大；人的处理满足不了需求，比如：定义很多很多的规则满足物体...

2018-03-24 17:27:31 346

原创 [Leetcode] Remove Duplicates from Sorted List II

描述Given a sorted linked list, delete all nodes that have duplicate numbers, leaving only distinct numbers from the original list.For example, Given 1->2->3->3->4->4->5, return 1->2->5. Given 1->1->1-

2017-01-11 20:16:42 341

原创 [Leetcode] Remove Duplicates from Sorted List

描述Given a sorted linked list, delete all duplicates such that each element appear only once.For example, Given 1->1->2, return 1->2. Given 1->1->2->3->3, return 1->2->3.将链表中的重复元素删掉。分析使用一个指针指向第一个元素，如果

2017-01-11 19:27:25 287

原创 [Leetcode] Rotate List

描述Given a list, rotate the list to the right by k places, where k is non-negative.For example: Given 1->2->3->4->5->NULL and k = 2, return 4->5->1->2->3->NULL.将一个链表向右循环位移 kk 位。分析1设 nn 表示链表长度，kk 表示右移次

2017-01-10 16:13:55 237

原创 [Leetcode] Swap Nodes in Pairs

描述Given a linked list, swap every two adjacent nodes and return its head.For example, Given 1->2->3->4, you should return the list as 2->1->4->3.Your algorithm should use only constant space. You may

2017-01-10 15:40:49 319

原创 [Leetcode] Merge Two Sorted Lists

描述Merge two sorted linked lists and return it as a new list. The new list should be made by splicing together the nodes of the first two lists.将两个有序链表合并。分析1这道题可以使用递归的方法来完成，当两个链表都非空时，将两个表头中值较小的一个加入答案，同时

2017-01-10 15:14:27 379

原创 [Leetcode] Remove Nth Node From End of List

描述Given a linked list, remove the nth node from the end of list and return its head.For example, Given linked list: 1->2->3->4->5, and n = 2. After removing the second node from the end, the linked

2017-01-09 23:24:04 283

原创 [Leetcode] Add Two Numbers

描述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

2017-01-09 23:12:26 265

原创 [Leetcode] Find All Duplicates in an Array

描述Given an array of integers, 1 ≤ a[i] ≤ n (n = size of array), some elements appear twice and others appear once.Find all the elements that appear twice in this array.Could you do it without extra spa

2017-01-08 11:36:36 264

原创 [Leectode] Game of Life

描述According to the Wikipedia’s article: “The Game of Life, also known simply as Life, is a cellular automaton devised by the British mathematician John Horton Conway in 1970.”Given a board with m by n

2017-01-08 11:03:53 324

原创 [Leetcode] Product of Array Except Self

描述Given an array of n integers where n > 1, nums, return an array output such that output[i] is equal to the product of all the elements of nums except nums[i].Solve it without division and in O(n).For

2017-01-08 10:16:08 242

原创 [Leetcode] Majority Element II

描述Given an integer array of size n, find all elements that appear more than ⌊ n/3 ⌋ times. The algorithm should run in linear time and in O(1) space.给定一个 nn 长数组，求出现次数大于 n/3n/3 的元素。分析首先分析说，解的数目最多为两个，因此我

2017-01-07 11:49:35 272

原创 [Leetcode] Summary Ranges

描述Given a sorted integer array without duplicates, return the summary of its ranges.For example, given [0,1,2,4,5,7], return ["0->2","4->5","7"].分析遍历一遍数组，每次记录起始位置以及最远能够合并的位置，同时还需判断能合并的是一个数还是一个序列。代码clas

2017-01-07 11:11:16 270

原创 [Leetcode] Combination Sum III

描述Find all possible combinations of k numbers that add up to a number n, given that only numbers from 1 to 9 can be used and each combination should be a unique set of numbers.Example 1:Input: k = 3, n

2017-01-07 10:34:27 231

原创 [Leetcode] Best Time to Buy and Sell Stock II

描述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 (ie, buy one a

2017-01-06 17:01:16 247

原创 [Leetcode] Triangle

描述Given a triangle, find the minimum path sum from top to bottom. Each step you may move to adjacent numbers on the row below.For example, given the following triangle[ [2], [3,4], [6,5,7],

2017-01-06 16:44:01 273

原创 [Leetcode] Construct Binary Tree from Inorder and Postorder Traversal

描述Given inorder and postorder traversal of a tree, construct the binary tree.Note: You may assume that duplicates do not exist in the tree.给定二叉树的后序遍历以及中序遍历，要求构造该二叉树。分析这是一道典型的分而治之的问题。二叉树的后序遍历的顺序是：左子数-右

2017-01-06 15:49:14 287

原创 [Leetcode] Construct Binary Tree from Preorder and Inorder Traversal

描述Given preorder and inorder traversal of a tree, construct the binary tree.Note: You may assume that duplicates do not exist in the tree.给定二叉树的前序遍历以及中序遍历，要求构造该二叉树。分析这是典型的分而治之的题目。二叉树的前序遍历的顺序是：节点-左子数-右

2017-01-06 15:39:55 327

原创 [Leetcode] Remove Duplicates from Sorted Array II

描述Follow up for “Remove Duplicates”: What if duplicates are allowed at most twice?For example, Given sorted array nums = [1,1,1,2,2,3],Your function should return length = 5, with the first five elem

2016-12-30 12:37:26 264

原创 [Leetcode] Word Search

描述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

2016-12-30 12:20:56 368

原创 [Leetcode] Unique Paths II

描述Follow up for “Unique Paths”:Now consider if some obstacles are added to the grids. How many unique paths would there be?An obstacle and empty space is marked as 1 and 0 respectively in the grid.For

2016-12-29 09:22:19 232

原创 [Leetcode] Unique Paths

描述A robot is located at the top-left corner of a m x n grid (marked ‘Start’ in the diagram below).The robot can only move either down or right at any point in time. The robot is trying to reach the bot

2016-12-29 09:13:01 237

原创 [Leetcode] Spiral Matrix II

描述Given an integer n, generate a square matrix filled with elements from 1 to n2 in spiral order.For example, Given n = 3,You should return the following matrix:[ [ 1, 2, 3 ], [ 8, 9, 4 ], [ 7, 6,

2016-12-29 09:05:57 213

原创 [Leetcode] Jump Game

描述Given an array of non-negative integers, you are initially positioned at the first index of the array.Each element in the array represents your maximum jump length at that position.Determine if you a

2016-12-29 09:00:56 231

原创 [Leetcode] Spiral Matrix

描述Given a matrix of m x n elements (m rows, n columns), return all elements of the matrix in spiral order.For example, Given the following matrix:[ [ 1, 2, 3 ], [ 4, 5, 6 ], [ 7, 8, 9 ]]You should

2016-12-28 14:58:47 279

原创 [Leetcode] Maximum Subarray

描述Find the contiguous subarray within an array (containing at least one number) which has the largest sum.For example, given the array [-2,1,-3,4,-1,2,1,-5,4], the contiguous subarray [4,-1,2,1] has t

2016-12-28 14:51:54 257

原创 [Leetcode] Rotate Image

描述You are given an n x n 2D matrix representing an image.Rotate the image by 90 degrees (clockwise).Follow up: Could you do this in-place?将一个二维 n∗nn*n 矩阵顺时针旋转 90°90° 。分析1这是一道很经典的题目，比较简单的做法是先对矩阵转置，然后对矩

2016-12-28 14:26:37 229

原创 [Leetcode] Combination Sum II

描述Given a collection of candidate numbers (C) and a target number (T), find all unique combinations in C where the candidate numbers sums to T.Each number in C may only be used once in the combination.

2016-12-28 13:50:06 246

原创 [Leetcode] Combination Sum

描述Given a set of candidate numbers (C) (without duplicates) and a target number (T), find all unique combinations in C where the candidate numbers sums to T.The same repeated number may be chosen from

2016-12-28 13:42:12 257

原创 [Leetcode] Search Insert Position

描述Given a sorted array and a target value, return the index if the target is found. If not, return the index where it would be if it were inserted in order.You may assume no duplicates in the array.Her

2016-12-27 23:10:30 240

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