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原创 Logistic回归的基本思想与公式推导

讲前小碎话Logistic回归是一种线性分类模型，通常用来解决线性二分类或多分类问题。无论是在李航老师的《统计学习方法》书中，还是在吴恩达老师的机器学习课程中，都是先假设随机变量x服从Logistic分布，即有如下的分布函数和概率密度函数：可是为什么定义这样的分布函数和概率密度函数，对于初学者来说，还是很难理解的。我们从Logistic回归的来源（也就是从贝叶斯学习发展来的）来理解...

2018-11-25 21:52:08 14493 1

原创 Deep Learning花书学习笔记-------第3章概率与信息论

第3章概率与信息论3.1 为什么使用概率频率派概率：概率直接与事件发生的频率相联系，如果一个事件发生的概率为p，p是可以通过反复试验由频率确定的。此时的概率p可以理解为一个参数可以通过试验确定。频率派进行推断时，依赖于数据的分布，以及试验观察获得的结果，通过似然函数进行推断。对于似然函数p(x|w)，频率派认为w是一个确定的参数，通过极大似然估计法确定w。贝叶斯概率：概率用来表示一种...

2019-03-13 00:00:28 323

原创找出数组中的重复数字--解题总结

题目数组长度为n + 1，数组中的数大小均在1~n的范围内，则数组中至少会存在一个重复数字。要求找出其中一个重复数组。例如，如果输入长度为7的数组{2,3,1,0,2,5,3}，那么对应的输出重复的数字是2或者3，输出其中一个即可。思路1：可直接将数组排序，遍历数组，找到其中一个重复数字即可。时间复杂度是O(nlogn)。def findDuplicates(nums): i...

2019-03-11 22:45:59 1978

原创 Deep Learning花书学习笔记-------第2章线性代数

第2章线性代数2.1 标量、向量、矩阵和张量标量（scalar）：标量是单独的数，只有大小没有方向。向量（vector）：向量是既有大小又有方向的量，它可以形象化地表示为带箭头的线段。一个向量是一个数列（有序排列的数）。可以把向量看作空间中的点，每个元素是不同坐标轴上的坐标。矩阵（matrix）：矩阵是一个二维数组。张量（tensor）:坐标超过两维的数组。数组元素分布在多...

2019-03-11 00:31:55 354

原创 LeetCode572. Subtree of Another Tree

题目描述：Given two non-empty binary trees s and t, check whether tree t has exactly the same structure and node values with a subtree of s. A subtree of s is a tree consists of a node in s and all of th...

2019-02-19 16:04:35 146

原创 LeetCode438. Find All Anagrams in a String

题目描述：Given a string s and a non-empty string p, find all the start indices of p's anagrams in s.Strings consists of lowercase English letters only and the length of both strings s and p will not b...

2019-02-19 15:05:40 79

原创 LeetCode437. Path Sum III

题目描述：You are given a binary tree in which each node contains an integer value.Find the number of paths that sum to a given value.The path does not need to start or end at the root or a leaf, but...

2019-02-19 11:30:44 125

原创 LeetCode101. Symmetric Tree

题目描述：Given a binary tree, check whether it is a mirror of itself (ie, symmetric around its center).For example, this binary tree [1,2,2,3,4,4,3] is symmetric: 1 / \ 2 2 / \ / \3 4 ...

2019-02-19 09:53:16 92

原创 LeetCode896. Monotonic Array ---Python三种思路

题目描述：An array is monotonic if it is either monotone increasing or monotone decreasing.An array A is monotone increasing if for all i <= j, A[i] <= A[j]. An array A is monotone decreasing if...

2019-01-29 22:54:23 193

原创 LeetCode763. Partition Labels

题目描述：A string S of lowercase letters is given. We want to partition this string into as many parts as possible so that each letter appears in at most one part, and return a list of integers represen...

2018-11-26 16:14:13 243

原创 LeetCode921. Minimum Add to Make Parentheses Valid

题目描述：Given a string S of '(' and ')' parentheses, we add the minimum number of parentheses ( '(' or ')', and in any positions ) so that the resulting parentheses string is valid.Formally, a parent...

2018-11-26 11:52:31 93

原创 LeetCode122. Best Time to Buy and Sell Stock II

题目描述：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 (i.e.,...

2018-11-25 22:21:57 96

原创 LeetCode860. Lemonade Change

题目描述：At a lemonade stand, each lemonade costs $5. Customers are standing in a queue to buy from you, and order one at a time (in the order specified by bills).Each customer will only buy one lem...

2018-11-23 18:27:25 109

原创 LeetCode455. Assign Cookies

题目描述：Assume you are an awesome parent and want to give your children some cookies. But, you should give each child at most one cookie. Each child i has a greed factor gi, which is the minimum size o...

2018-11-23 17:05:23 91

原创 LeetCode605. Can Place Flowers

class Solution: """ :type flowerbed: List[int] :type n: int :rtype: bool """ def canPlaceFlowers(self, flowerbed, n): i = sum = 0 if n == 0: return ...

2018-04-25 13:20:15 159

原创 LeetCode169. Majority Element

Given an array of size n, find the majority element. The majority element is the element that appears more than ⌊ n/2 ⌋ times.You may assume that the array is non-empty and the majority element always...

2018-04-11 12:07:16 108

原创 LeetCode 561. Array Partition I

Given an array of 2n integers, your task is to group these integers into n pairs of integer, say (a1, b1), (a2, b2), ..., (an, bn) which makes sum of min(ai, bi) for all i from 1 to n as large as poss...

2018-04-09 19:14:38 150 1

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