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RSS订阅原创 Number of 1 Bits
191.Number of 1 BitsWrite a function that takes an unsigned integer and returnthe number of '1'bits it has (also known as theHamming weight).Example 1:Input: 0000000000000000000000000000...
2019-03-28 10:04:50
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原创 Excel Sheet Column Number
171.Excel Sheet Column NumberGiven a column title as appear in an Excel sheet, return its corresponding column number.For example: A -> 1 B -> 2 C -> 3 ... Z -&g...
2019-03-28 09:43:15
221
原创 Search in Rotated Sorted Array
33.Search in Rotated Sorted ArraySuppose 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...
2019-03-22 16:15:17
232
原创 Unique Binary Search Trees II
95.Unique Binary Search Trees IIGiven an integern, generate all structurally uniqueBST's(binary search trees) that store values 1 ...n.Example:Input: 3Output:[ [1,null,3,2], [3,2,...
2019-03-22 15:43:26
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原创 Decode Ways
91.Decode WaysA message containing letters fromA-Zis being encoded to numbers using the following mapping:'A' -> 1'B' -> 2...'Z' -> 26Given anon-emptystring containing only...
2019-03-20 11:22:08
157
原创 Minimum Path Sum
64.Minimum Path SumGiven amxngrid filled with non-negative numbers, find a path from top left to bottom right whichminimizesthe sum of all numbers along its path.Note:You can only move eit...
2019-03-19 17:14:04
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原创 Unique Paths II
63.Unique Paths IIA robot is located at the top-left corner of amxngrid (marked 'Start' in the diagram below).The robot can only move either down or right at any point in time. The robo...
2019-03-19 15:36:06
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原创 Unique Paths
62.Unique PathsA robot is located at the top-left corner of amxngrid (marked 'Start' in the diagram below).The robot can only move either down or right at any point in time. The robot is t...
2019-03-19 11:58:55
121
原创 Longest Palindromic Substring
5.Longest Palindromic SubstringGiven a strings, find the longest palindromic substring ins. You may assume that the maximum length ofsis 1000.Example 1:Input: "babad"Output: "bab...
2019-03-19 11:33:00
133
原创 Min Cost Climbing Stairs
746.Min Cost Climbing StairsOn a staircase, thei-th step has some non-negative costcost[i]assigned (0 indexed).Once you pay the cost, you can either climb one or two steps. You need to find...
2019-03-15 22:24:35
127
原创 Range Sum Query - Immutable
303.Range Sum Query - ImmutableGiven an integer arraynums, find the sum of the elements between indicesiandj(i≤j), inclusive.Example:Given nums = [-2, 0, 3, -5, 2, -1]sumRange(0, 2) -...
2019-03-14 21:56:51
153
原创 House Robber
198.House RobberYou are a professional robber planning to rob houses along a street. Each house has a certain amount of money stashed, the only constraint stopping you from robbing each of them is ...
2019-03-14 21:23:18
125
原创 Two Sum IV - Input is a BST
653.Two Sum IV - Input is a BSTGiven a Binary Search Tree and a target number, return true if there exist two elements in the BST such that their sum is equal to the given target.Example 1:...
2019-03-14 20:48:51
122
原创 Average of Levels in Binary Tree
637.Average of Levels in Binary TreeGiven a non-empty binary tree, return the average value of the nodes on each level in the form of an array.Example 1:Input: 3 / \ 9 20 / \...
2019-03-14 18:02:23
156
原创 Path Sum III
437.Path Sum IIIYou 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...
2019-03-14 17:57:26
124
原创 最大字段和
Given an integer arraynums, find the contiguous subarray(containing at least one number) which has the largest sum and return its sum.Example:Input: [-2,1,-3,4,-1,2,1,-5,4],Output: 6Explanati...
2019-03-08 09:43:20
238
原创 Sum of Left Leaves
404.Sum of Left LeavesFind the sum of all left leaves in a given binary tree.Example: 3 / \ 9 20 / \ 15 7There are two left leaves in the binary tree, with values 9 and...
2019-03-07 21:54:46
200
原创 Subtree of Another Tree
572.Subtree of Another Tree判断一棵树是否为另外一颗树的子树。1、最开始的思路就是比较每个节点，判断其对应的树是不是和另外一棵树相等。那如何去比较每个点呢。一开始没想出来，其实就是写一个tranverse函数，每次判断当前节点耳朵树，以及其左子树，以及其右子树，用或连接，递归。//对每一个节点都求一次，两棵树是不是相等class Soluti...
2019-03-07 17:01:39
154
原创 Binary Tree Paths
257.Binary Tree PathsGiven a binary tree, return all root-to-leaf paths.Note:A leaf is a node with no children.Example:Input: 1 / \2 3 \ 5Output: ["1->2->5", "1-&g...
2019-03-07 14:56:25
144
原创 Binary Tree Tilt
563.Binary Tree TiltGiven a binary tree, return the tilt of thewhole tree.The tilt of atree nodeis defined as theabsolute differencebetween the sum of all left subtree node values and the su...
2019-03-07 11:19:32
193
原创 Diameter of Binary Tree
543.Diameter of Binary TreeGiven a binary tree, you need to compute the length of the diameter of the tree. The diameter of a binary tree is the length of thelongestpath between any two nodes ...
2019-03-07 10:24:44
113
原创 Lowest Common Ancestor of a Binary Search Tree
235.Lowest Common Ancestor of a Binary Search TreeGiven a binary search tree (BST), find the lowest common ancestor (LCA) of two given nodes in the BST.According to thedefinition of LCA on Wi...
2019-03-07 10:21:34
131
原创 Invert Binary Tree
#226.Invert Binary Tree递归反转，申明一个temp结点/** * Definition for a binary tree node. * struct TreeNode { * int val; * TreeNode *left; * TreeNode *right; * TreeNode(int x) :...
2019-03-07 10:19:04
114
原创 Majority Element
#169Majority ElementGiven an array of sizen, find the majority element. The majority element is the element that appearsmore than⌊ n/2 ⌋times.You may assume that the array is non-empty and th...
2019-03-05 21:11:21
147
原创 Excel Sheet Column Title
168.Excel Sheet Column TitleGiven a positive integer, return its corresponding column title as appear in an Excel sheet.For example: 1 -> A 2 -> B 3 -> C ... 26 ...
2019-03-05 20:01:47
172
原创 Two Sum II - Input array is sorted
#167Two Sum II - Input array is sortedGiven an array of integers that is alreadysorted in ascending order, find two numbers such that they add up to a specific target number.The function twoSum ...
2019-03-05 17:16:34
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原创 Intersection of Two Linked Lists
#160Intersection of Two Linked Lists求两个链表的公共节点。1、分别遍历两个链表，求各自长度。然后求长度差，并让长的先走长度差这么多步，然后同时开始走，判断每个结点是否相等。（考虑到公共节点之后的每个结点一定是相等的，所以两个有公共节点的链表一定是前面不同。）class Solution {public: ListNode *get...
2019-03-05 15:54:14
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原创 sklearn之adaboost
# -*- coding: utf-8 -*-import pandasimport numpy as npimport matplotlib.pyplot as pltfrom sklearn.ensemble import AdaBoostClassifierfrom sklearn.tree import DecisionTreeClassifierfrom sklear...
2019-03-01 10:13:29
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原创 盛最多水的容器
#20 盛最多水的容器题目描述：给定n个非负整数a1，a2，...，an，每个数代表坐标中的一个点(i,ai) 。在坐标内画n条垂直线，垂直线i的两个端点分别为(i,ai) 和 (i, 0)。找出其中的两条线，使得它们与x轴共同构成的容器可以容纳最多的水。说明：你不能倾斜容器，且n的值至少为 2。输入: [1,8,6,2,5,4,8,3,7]...
2019-02-28 22:19:10
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原创 删除排序数组中的重复项
#20 删除排序数组中的重复项题目描述：给定一个排序数组，你需要在原地删除重复出现的元素，使得每个元素只出现一次，返回移除后数组的新长度。不要使用额外的数组空间，你必须在原地修改输入数组并在使用 O(1) 额外空间的条件下完成。给定数组 nums = [1,1,2], 函数应该返回新的长度 2, 并且原数组 nums 的前两个元素被修改为 1,2，你不需要考虑数组中超出...
2019-02-28 21:17:48
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原创 有效的括号
#20 有效的括号题目描述：给定一个只包括'('，')'，'{'，'}'，'['，']'的字符串，判断字符串是否有效。有效字符串需满足：左括号必须用相同类型的右括号闭合。左括号必须以正确的顺序闭合。注意空字符串可被认为是有效字符串。输入: "()"输出: true输入: "()[]{}"输出: true输入: "(]"输出: false输入: "([)...
2019-02-28 20:55:35
158
转载 BT,GBDT相关博客
https://blog.youkuaiyun.com/weixin_28750267/article/details/81056866
2019-02-28 17:26:38
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原创 Longest Common Prefix
#14 Longest Common Prefix最大公共前缀。注意不是字符串，是前缀，因此会方便很多。如输入["flower","flow","flight"]，返回字符串"fl"；若没有，则返回空字符串。1、对所有字符串二分查找公共字符串+递归。去找前面一半的公共字符串和后面一般的公共字符串，再去找他们的公共字符串。以此不断二分下去，递归查找。最后肯定归结到判断2个字符串的...
2019-02-25 16:12:02
344
原创 Roman to Integer
#13 Roman to Integer罗马数恢复成整数。其实就是把几个特例写出来就可以，否则就加上去。注意因为遇到了I就+1，因此判断其后若跟着IV，则再+3而不是+4，其他同理。class Solution {public: int romanToInt(string s) { if(s.size()==0) return 0; int nu...
2019-02-25 15:53:51
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原创 Palindrome Number
#9 Palindrome Number判断回文数。1、上一题就做过反转一个数，因此第一个思路就是反转数，如果和原数相等则为回文数。class Solution {public: bool isPalindrome(int x) { if(x<0) return 0; int originNum=x; int revNu...
2019-02-25 15:51:03
110
原创 Reverse Integer
#7 Reverse Integer反转数字。基本思路就是利用求余%和求商/两个计算。每次计算完的余在新的循环次数里面要乘以10，再加上新的余。利用商去更新每次数。同时考虑到32bit有无溢出。C++的<stdint.h>里面定义好了INT32_MAX和INT32_MIN。当然INT64_MAX也有。int64_t 其实就相当于long long; int32_t就是int...
2019-02-25 15:45:10
109
原创 Two Sum
前天开始刷leetcode，所以打算把代码和一些思路写在这里吧。本身自己就是菜鸟，就从easy开始做，大部分都是可以直接想到思路的。先把这几天的上传上来。#1Two Sum给出整型数组和一个数，找到数组中两个相加为该数的不同数的索引，答案唯一。1、暴力法暴力法就是逐个去遍历该元素和后面的元素之和，找到则返回即可。class Solution {public: v...
2019-02-25 15:36:45
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原创 信号DOA估计
DOA估计（或波达方向估计）：将接受信号进行空间傅里叶变换（空间傅里叶变换和离散时间傅里叶变换的区别是，空间傅里叶变换的求和是对阵元空间位置m，而时域傅里叶变换的求和变量时离散时间n），进而取模的平方得到空间谱，估计出信号的到达方向（空间谱的最大值对应的相位φ，再根据定义φ=2πdsinθ/λ，计算θ）。1、概念假设均匀线阵，空间仅有一个信号源，则接受信号可以表示为： ...
2018-07-09 12:05:12
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原创 卡尔曼滤波估计线性预测器最优权值
卡尔曼滤波在维纳滤波中的应用考虑到最优权值是一个常值向量，因此状态方程为w(n)=w(n-1)观测方程就是由滤波器的最优滤波误差推导出:d(n)=uT(n)w*(n)+e(n)然后对应到观测方程和状态方程 仿真时的权向量初始值为[0 0]T，估计误差相关矩阵P的初始值为I；假设信号u(n)由一个四阶AR模型产生:u(n)-1.6u(n-1)+1.46u(n-2)-0...
2018-07-09 11:33:33
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原创 RLS实现求解最小二乘确定性正则方程
RLS算法：递归最小二乘算法，使用迭代的方法求解最小二乘的确定性正则方程（奇异值分解也可以）。在用RLS时，数据矩阵会进一步得到扩充，将每次观测数据都放进来，而不是像奇异值分解只将每个滤波器都有数据时作为开始。这里就不多写RLS的推导过程；大致写一些思路：根据扩展后的观测数据矩阵A，定义出随时间和样本两个变化的时间相关矩阵和时间互相关矩阵，代入确定性正则方程；考虑到离当前时刻近的观测值对相关矩阵和...
2018-07-09 11:13:48
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