<?xml version="1.0" encoding="utf-8" ?><rss version="2.0"><channel><title><![CDATA[Eliot的博客]]></title><description><![CDATA[]]></description><link>https://blog.youkuaiyun.com/monochrome00</link><language>zh-cn</language><generator>https://blog.youkuaiyun.com/</generator><copyright><![CDATA[Copyright &copy; monochrome00]]></copyright><item><title><![CDATA[【DP】ICPC Pacific Northwest Regional Contest 2019 - F - Carny Magician]]></title><link>https://blog.youkuaiyun.com/monochrome00/article/details/105921913</link><guid>https://blog.youkuaiyun.com/monochrome00/article/details/105921913</guid><author>monochrome00</author><pubDate>Mon, 04 May 2020 19:38:51 +0800</pubDate><description><![CDATA[题目链接https://www.jisuanke.com/contest/8291?view=challenges

题意
询问长度为 nnn ，满足 mmm 个下标与数值匹配的，字典序第k小的排序。

题解
大概也就写了一万个 dpdpdp 吧。
c[i][j]c[i][j]c[i][j] 表示 iii 个位置挑出 jjj 个的方案数，也就是组合数。
fac[i]fac[i]fac[i] 表示 ...]]></description><category></category></item><item><title><![CDATA[【概率DP】Gym - 101174 - D - Dinner Bet]]></title><link>https://blog.youkuaiyun.com/monochrome00/article/details/105185055</link><guid>https://blog.youkuaiyun.com/monochrome00/article/details/105185055</guid><author>monochrome00</author><pubDate>Sun, 29 Mar 2020 20:11:55 +0800</pubDate><description><![CDATA[题目链接http://codeforces.com/gym/101174
题意
NNN 个球标号为 111 到 NNN，两个人分别写下 CCC 个数字，每次随机选出 DDD 个球，若干次后，如果某个人写的 CCC 个数字都出现过，则游戏结束。问游戏持续回合数的期望。

题解
概率DP。
dp[i][j][k]dp[i][j][k]dp[i][j][k] 的状态表示两个人的公共数字有 kkk 个还没...]]></description><category></category></item><item><title><![CDATA[【画画】UCF Local Programming Contest 2012（Practice）E. Pete's Pantry]]></title><link>https://blog.youkuaiyun.com/monochrome00/article/details/104664869</link><guid>https://blog.youkuaiyun.com/monochrome00/article/details/104664869</guid><author>monochrome00</author><pubDate>Wed, 04 Mar 2020 22:52:21 +0800</pubDate><description><![CDATA[题目链接https://www.jisuanke.com/contest/7332

纯粹的画画题
此生再也不愿意做这种题（流泪）

#include&lt;bits/stdc++.h&gt;
using namespace std;
typedef long double db;
const int N=1e3+7;
int t,cs;
int n;
vector&lt;string&gt;vc...]]></description><category></category></item><item><title><![CDATA[【概率DP】Gym - 102470 - D - Darts]]></title><link>https://blog.youkuaiyun.com/monochrome00/article/details/104300516</link><guid>https://blog.youkuaiyun.com/monochrome00/article/details/104300516</guid><author>monochrome00</author><pubDate>Thu, 13 Feb 2020 18:42:40 +0800</pubDate><description><![CDATA[题目链接http://codeforces.com/gym/102470/problem/D

D - Darts

题意
AAA 和 BBB 两个人比赛射飞镖，规则如下：
两个人轮流射飞镖，初始分数都为NNN，假设射中区域 xxx，如果 x≤Nx\le Nx≤N，分数减去 xxx；否则分数保持不变。第一个把分数清零的玩家获胜。
AAA 每次随便射飞镖，所以他射到每个区域的概率都相等。
BBB 有...]]></description><category></category></item><item><title><![CDATA[【哈希】Gym - 102448 - C - Call from Mendes]]></title><link>https://blog.youkuaiyun.com/monochrome00/article/details/104172928</link><guid>https://blog.youkuaiyun.com/monochrome00/article/details/104172928</guid><author>monochrome00</author><pubDate>Tue, 04 Feb 2020 18:12:20 +0800</pubDate><description><![CDATA[题目链接http://codeforces.com/gym/102448/problem/C

题意
三种操作，一共有QQQ个：

1  X1\;X1X：在字典里插入字符串 XXX
2  X2\;X2X：在字典里删除字符串 XXX
3  X3\; X3X：输出字典中最短的且前缀是 XXX 的下标。如果有多个字符串，输出字典序最小的。

字符串的下标是指该串被插入时的时间。
输入中所有的字符串长度和...]]></description><category></category></item><item><title><![CDATA[【并查集】Codeforces Round #616 (Div. 2) - E. Prefix Enlightenment]]></title><link>https://blog.youkuaiyun.com/monochrome00/article/details/104158583</link><guid>https://blog.youkuaiyun.com/monochrome00/article/details/104158583</guid><author>monochrome00</author><pubDate>Mon, 03 Feb 2020 17:11:44 +0800</pubDate><description><![CDATA[题目链接http://codeforces.com/contest/1291/problem/E

题意
给出一个长度为nnn的010101串SSS表示初始状态。
给出kkk个集合，集合内的元素是111~nnn，表示SSS的下标。保证任意三个不同集合的交为空集。
每次操作可以选择一个集合，使得集合内所有下标的状态SSS翻转。
询问要使得状态SSS前iii位都为111所需要的最少操作次数。
题目保证...]]></description><category></category></item><item><title><![CDATA[【吴恩达机器学习】正则化  Regularization]]></title><link>https://blog.youkuaiyun.com/monochrome00/article/details/104125072</link><guid>https://blog.youkuaiyun.com/monochrome00/article/details/104125072</guid><author>monochrome00</author><pubDate>Sat, 01 Feb 2020 21:03:47 +0800</pubDate><description><![CDATA[正则化 （Regularization）
过拟合问题（The Problem of Overfitting）


左边的算法没有很好地拟合训练集，这个问题称作欠拟合(underfitting)，也可以说该算法具有高偏差(high bias)
中间的算法拟合效果不错，是理想的模型
右边的算法几乎完美地拟合了训练集，它的代价函数也可能接近于0，但是它最后给出的模型并不好。这就是过拟合(Overfitt...]]></description><category></category></item><item><title><![CDATA[【吴恩达机器学习】逻辑回归 Python实现]]></title><link>https://blog.youkuaiyun.com/monochrome00/article/details/104138089</link><guid>https://blog.youkuaiyun.com/monochrome00/article/details/104138089</guid><author>monochrome00</author><pubDate>Sat, 01 Feb 2020 20:35:04 +0800</pubDate><description><![CDATA[逻辑回归（Logistic Regression）
梯度下降版本
吴恩达课程给出来的数据因为是给优化跑的，普通的梯度下降跑不出来，除非初始值设[−100,1,1][-100,1,1][−100,1,1]这样的。
import numpy as np
import pandas as pd
import matplotlib.pyplot as plt


# 获取数据
def getData():...]]></description><category></category></item><item><title><![CDATA[【吴恩达机器学习】逻辑回归 Logistic Regression]]></title><link>https://blog.youkuaiyun.com/monochrome00/article/details/104109806</link><guid>https://blog.youkuaiyun.com/monochrome00/article/details/104109806</guid><author>monochrome00</author><pubDate>Wed, 29 Jan 2020 20:20:27 +0800</pubDate><description><![CDATA[逻辑回归（Logistic Regression）
对于分类问题(Classification problem)，也就是预测的变量 yyy 是一个离散值（比如y={0,1}y=\{0, 1\}y={0,1}），可以使用**逻辑回归(Logistic Regression)**来处理。逻辑回归的假设函数满足：0≤hθ(x)≤10\le h_\theta (x)\le 10≤hθ​(x)≤1
假设函数...]]></description><category></category></item><item><title><![CDATA[【吴恩达机器学习】线性回归 Python实现]]></title><link>https://blog.youkuaiyun.com/monochrome00/article/details/104100908</link><guid>https://blog.youkuaiyun.com/monochrome00/article/details/104100908</guid><author>monochrome00</author><pubDate>Tue, 28 Jan 2020 17:11:56 +0800</pubDate><description><![CDATA[1. 单变量线性回归
import numpy as np
import pandas as pd
import matplotlib.pyplot as plt


# 获取假设函数
def getHypothesis(X, theta):
    return X * theta.T


# 获取代价函数
def getCost(X, y, theta):
    return np.sum(...]]></description><category></category></item><item><title><![CDATA[【吴恩达机器学习】线性回归 Linear Regression]]></title><link>https://blog.youkuaiyun.com/monochrome00/article/details/104077303</link><guid>https://blog.youkuaiyun.com/monochrome00/article/details/104077303</guid><author>monochrome00</author><pubDate>Thu, 23 Jan 2020 19:39:18 +0800</pubDate><description><![CDATA[线性回归(Linear Regression)

单变量线性回归 (Linear regression with one variable / Univariate linear regression)
多变量线性回归 (Linear regression with multiple variables / Multivariate linear regression)

标记符号:

mmm —...]]></description><category></category></item><item><title><![CDATA[吴恩达机器学习目录]]></title><link>https://blog.youkuaiyun.com/monochrome00/article/details/104077287</link><guid>https://blog.youkuaiyun.com/monochrome00/article/details/104077287</guid><author>monochrome00</author><pubDate>Thu, 23 Jan 2020 19:07:55 +0800</pubDate><description><![CDATA[绪论
机器学习定义

Arthur Samuel(1959): Field of study that gives computers the ability to learn without being explicitly programmed.
Tom Mitchell(1998): A computer program is said to learn from experience EE...]]></description><category></category></item><item><title><![CDATA[【树剖】Codeforces Round #601 (Div. 1) - D. Tree Queries]]></title><link>https://blog.youkuaiyun.com/monochrome00/article/details/103191890</link><guid>https://blog.youkuaiyun.com/monochrome00/article/details/103191890</guid><author>monochrome00</author><pubDate>Thu, 21 Nov 2019 22:24:06 +0800</pubDate><description><![CDATA[题目链接https://codeforces.com/contest/1254/problem/D

题意
给出一棵树，每个点都有权值，初始都为0，有两个操作

给出v,dv,dv,d，等概率随机一个点rrr，对于所有的点uuu，uuu到rrr的路径上经过点vvv。对于所有的这些点uuu权值加上ddd。
求点vvv的权值期望

1&lt;=n,q&lt;=1500001&lt;=n,q&lt;=1...]]></description><category></category></item><item><title><![CDATA[【支配树】2014-2015 ACM-ICPC, NEERC, Southern Subregional Contest - L. Useful Roads]]></title><link>https://blog.youkuaiyun.com/monochrome00/article/details/102913645</link><guid>https://blog.youkuaiyun.com/monochrome00/article/details/102913645</guid><author>monochrome00</author><pubDate>Tue, 05 Nov 2019 12:53:18 +0800</pubDate><description><![CDATA[题目链接https://codeforces.com/gym/100513/problem/L

题意
在有向图上每个节点只经过一次的路径称为简单路
给出一张有向图，一条边是好的，当且仅当存在一条由1号节点出发的简单路包含这条边。
问哪些边是好的。

题解
支配树模板题，支配树上的返祖边都是坏边。

#include&lt;bits/stdc++.h&gt;
using namespace std...]]></description><category></category></item><item><title><![CDATA[P5540 【模板】最小乘积生成树]]></title><link>https://blog.youkuaiyun.com/monochrome00/article/details/102856928</link><guid>https://blog.youkuaiyun.com/monochrome00/article/details/102856928</guid><author>monochrome00</author><pubDate>Fri, 01 Nov 2019 14:54:10 +0800</pubDate><description><![CDATA[题目链接https://www.luogu.org/problem/P5540

题意
给出一个 nnn 个点 mmm 条边的无向图，第 iii 条边有两个权值 aia_iai​和bib_ibi​
求该图的一棵生成树 TTT ，使得(∑ae)∗(∑be)\sum a_e)*(\sum b_e)∑ae​)∗(∑be​)最小。

题解

https://www.luogu.org/problemnew...]]></description><category></category></item><item><title><![CDATA[【树的哈希/树同构】2019-2020 ICPC, Asia Jakarta Regional Contest - F. Regular Forestation]]></title><link>https://blog.youkuaiyun.com/monochrome00/article/details/102834706</link><guid>https://blog.youkuaiyun.com/monochrome00/article/details/102834706</guid><author>monochrome00</author><pubDate>Thu, 31 Oct 2019 11:34:17 +0800</pubDate><description><![CDATA[题目链接https://codeforces.com/contest/1252/problem/F

题意
给出一棵树，问删去一个度大于1的节点，使得剩下的树两两同构。问剩下的树最多是多少。

题解
容易想到，能够删去的点不可能存在多个，而且删去的必然是树的重心。剩下就是个判树同构了，而这个可以直接对树进行哈希来判断。

关于树的哈希与判树同构：https://www.luogu.org/prob...]]></description><category></category></item><item><title><![CDATA[【线段树优化建图+最短路】Codeforces Round #406 (Div. 1) - B. Legacy]]></title><link>https://blog.youkuaiyun.com/monochrome00/article/details/102781462</link><guid>https://blog.youkuaiyun.com/monochrome00/article/details/102781462</guid><author>monochrome00</author><pubDate>Mon, 28 Oct 2019 15:16:29 +0800</pubDate><description><![CDATA[题目链接https://codeforces.com/problemset/problem/786/B

题意
一共有nnn个点，三种建边方式：

点uuu向点vvv建一条权值为www的边
点uuu到[l,r][l,r][l,r]内的点建一条权值为www的边
[l,r][l,r][l,r]内的点到点vvv建一条权值为www的边

一共要加mmm次边，问从点sss到所有点的最短路。1≤n,m≤1e5...]]></description><category></category></item><item><title><![CDATA[【仙人掌直径】P4244 [SHOI2008]仙人掌图 II]]></title><link>https://blog.youkuaiyun.com/monochrome00/article/details/102680499</link><guid>https://blog.youkuaiyun.com/monochrome00/article/details/102680499</guid><author>monochrome00</author><pubDate>Tue, 22 Oct 2019 13:26:15 +0800</pubDate><description><![CDATA[题目链接https://www.luogu.org/problem/P4244

题意
仙人掌：无向图，任何一条边至多在一个环内。
直径：任意两点最短路(边权为111)的最大值。

题解
普通树上求直径可以写成dpdpdp的形式，dp[u]dp[u]dp[u]代表uuu子树内以uuu为端点的最长链，树形dpdpdp做一遍搜索即可。

答案更新为：ans=max(dp[u]+dp[v]+1)ans=...]]></description><category></category></item><item><title><![CDATA[【想法】2013-2014 ACM-ICPC, NEERC, Moscow Subregional Contest - K - Top K Elements]]></title><link>https://blog.youkuaiyun.com/monochrome00/article/details/102543343</link><guid>https://blog.youkuaiyun.com/monochrome00/article/details/102543343</guid><author>monochrome00</author><pubDate>Mon, 14 Oct 2019 10:55:43 +0800</pubDate><description><![CDATA[题目链接https://codeforces.com/gym/100257

题意
给出一个递推式xi=(A⋅xi−2+B⋅xi−1+C)mod231x_i = (A · x_{i−2} + B · x_{i−1} + C) mod 2^{31}xi​=(A⋅xi−2​+B⋅xi−1​+C)mod231，问你求出前nnn项的前kkk大。
1≤n≤1e8,1≤k≤2e51\leq n \leq 1e...]]></description><category></category></item><item><title><![CDATA[【SA+ST+二分+DP】Codeforces Round #543 Div. 1 - C. Compress String]]></title><link>https://blog.youkuaiyun.com/monochrome00/article/details/102499832</link><guid>https://blog.youkuaiyun.com/monochrome00/article/details/102499832</guid><author>monochrome00</author><pubDate>Fri, 11 Oct 2019 14:04:41 +0800</pubDate><description><![CDATA[题目链接https://codeforces.com/problemset/problem/1120/C

题意
给出一串字符串，将它拆成一些子串拼接。任何一个子串的价值都可以是aaa，如果某个子串tit_iti​是字符串t1t2..ti−1t_1t_2..t_{i-1}t1​t2​..ti−1​的子串，它的价值可以是bbb。问价值最小是多少

题解
从后往前dpdpdp，如果s[i,j]s[i,...]]></description><category></category></item></channel></rss>