【Power of Two】cpp
摘要：题目：Given an integer, write a function to determine if it is a power of two.代码：class Solution {public: bool isPowerOfTwo(int n) { if ( n>...
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posted @ 2015-07-22 07:23
07 2015 档案
【Binary Search Tree Iterator 】cpp
摘要：题目：Implement an iterator over a binary search tree (BST). Your iterator will be initialized with the root node of a BST.Callingnext()will return the n...
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posted @ 2015-07-14 19:25
【Binary Tree Right Side View 】cpp
摘要：题目：Given a binary tree, imagine yourself standing on therightside of it, return the values of the nodes you can see ordered from top to bottom.For exa...
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posted @ 2015-07-14 18:39
【Count Complete Tree Nodes】cpp
摘要：题目：Given acompletebinary tree, count the number of nodes.Definition of a complete binary tree fromWikipedia:In a complete binary tree every level, exc...
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posted @ 2015-07-14 17:25
【Kth Smallest Element in a BST 】cpp
摘要：题目：Given a binary search tree, write a functionkthSmallestto find thekth smallest element in it.Note:You may assume k is always valid, 1 ≤ k ≤ BST's t...
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posted @ 2015-07-14 13:00
【Invert Binary Tree】cpp
摘要：题目：Invert Binary TreeTotal Accepted:20346Total Submissions:57084My SubmissionsQuestionSolutionInvert a binary tree. 4 / \ 2 7 / \ / \1 ...
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posted @ 2015-07-14 12:48
【Lowest Common Ancestor of a Binary Search Tree】cpp
摘要：题目：Given a binary search tree (BST), find the lowest common ancestor (LCA) of two given nodes in the BST.According to thedefinition of LCA on Wikipedi...
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posted @ 2015-07-14 12:35
【Lowest Common Ancestor of a Binary Tree】cpp
摘要：题目：Given a binary tree, find the lowest common ancestor (LCA) of two given nodes in the tree.According to thedefinition of LCA on Wikipedia: “The lowe...
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posted @ 2015-07-14 10:55
【Support Vector Regression】林轩田机器学习技法
摘要：上节课讲了Kernel的技巧如何应用到Logistic Regression中。核心是L2 regularized的error形式的linear model是可以应用Kernel技巧的。这一节，继续沿用representer theorem，延伸到一般的regression问题。首先想到的就是rid...
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posted @ 2015-07-13 16:40
【Balanced Binary Tree】cpp
摘要：题目：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 de...
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posted @ 2015-07-12 14:17
【Kernel Logistic Regression】林轩田机器学习技术
摘要：最近求职真慌，一方面要看机器学习，一方面还刷代码。还是静下心继续看看课程，因为觉得实在讲的太好了。能求啥样搬砖工作就随缘吧。这节课的核心就在如何把kernel trick到logistic regression上。首先把松弛变量的表达形式修改一下，把constrained的形式改成unconstra...
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posted @ 2015-07-09 17:32
【作业一】林轩田机器学习技术
摘要：关注的是编程题目Q15~Q20这里需要借用libsvm的python包，需要一下几个处理步骤：（1）到libsvm官网（http://www.csie.ntu.edu.tw/~cjlin/libsvm/）下载.gz包，解压缩到一个目录（2）在解压的根目录make命令（3）再到解压缩根目录下的pyth...
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posted @ 2015-07-07 22:38
【Soft-Margin Support Vector Machine】林轩田机器学习技术
摘要：Hard-Margin的约束太强了：要求必须把所有点都分开。这样就可能带来overfiiting，把noise也当成正确的样本点了。Hard-Margin有些“学习洁癖”，如何克服这种学习洁癖呢？沿用pocket算法的思想，修改一下优化目标函数的形式，补上一个错分点的惩罚项CΣ...。（1）C越大，...
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posted @ 2015-07-05 17:16
【Kernal Support Vector Machine】林轩田机器学习技术
摘要：考虑dual SVM 问题：如果对原输入变量做了non-linear transform，那么在二次规划计算Q矩阵的时候，就面临着：先做转换，再做内积；如果转换后的项数很多（如100次多项式转换），那么耗费的时间就比较多。能否在计算Q矩阵这一步的时候，把transform+inner product...
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posted @ 2015-07-05 10:16
【Dual Support Vector Machine】林轩田机器学习技法
摘要：这节课内容介绍了SVM的核心。首先，既然SVM都可以转化为二次规划问题了，为啥还有有Dual啥的呢？原因如下：如果x进行non-linear transform后，二次规划算法需要面对的是d`+1维度的N个变量，以及N个约束如果d`的维度超大，那么二次规划解起来的代价就太大了。因此，SVM的精髓就在...
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posted @ 2015-07-03 22:33
【Linear Support Vector Machine】林轩田机器学习技法
摘要：首先从介绍了Large_margin Separating Hyperplane的概念。（在linear separable的前提下）找到largest-margin的分界面，即最胖的那条分界线。下面开始一步步说怎么找到largest-margin separating hyperplane。接下来...
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posted @ 2015-07-02 20:45
【作业4】林轩田机器学习基石
摘要：作业四的代码题目主要是基于ridge regression来做的，并加上了各种cross-validation的情况。由于ridge regression是有analytic solution，所以直接求逆矩阵就OK了，过程并不复杂。只有在做cross-validation的时候遇上了些问题。#en...
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posted @ 2015-07-01 19:33
