传送门 题目大意 https://www.luogu.org/problemnew/show/CF997D 分析 我们发现两棵树互不相关 于是我们可以分别求出两棵树的信息 我们点分,人啊按后设f[i][x]为从根出发走i步到x中间不经过根的方案数,g[i][x]为可以经过根的方案数 代码 #include<iostream> #include<cstdio> #include<cstring> #include<string> #include<alg…

Codeforces 题面传送门 & 洛谷题面传送门 一种换根 dp 的做法. 首先碰到这类题目,我们很明显不能真的把图 \(G\) 建出来,因此我们需要观察一下图 \(G\) 有哪些性质.很明显我们可以把它看作 \(T_1,T_2\) 上分别有一个标记,每次可以将 \(T_1,T_2\) 上的某个标记沿着某条边移动一步,问 \(k\) 步之后标记刚好回到原位的方案数是多少. 显然两棵树是独立的,因此可以分开来考虑,我们记 \(dp1_{i,j}\) 表示 \(T_1\) 中从 \(i\) 开始…

题目大意: 给两个树,求环的个数. 题目分析: 出题人摆错题号系列. 通过画图很容易就能想到把新图拆在两个树上,在树上游走成环. 考虑DP状态F,G,T.F表示最终答案,T表示儿子不考虑父亲,G表示父亲不考虑儿子.T通过从下往上做NTT,G通过从上往下做NTT.F顺便做NTT. 最后做一下拼接就行. 代码: #include<bits/stdc++.h> using namespace std; ; ; ; ],k; vector <][maxn]; ][maxn][],gi[][max…

Posted by Marty Cagan on August 28, 2007 Tags: product management, product marketing, program management, product discovery Industry pundits claim that 9 out of 10 product releases are failures in that they don’t meet their goals.  I don’t know if th…

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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 example, given [1,2,3,4], return [24,12,8,6]. Fo…

Find the contiguous subarray within an array (containing at least one number) which has the largest product. For example, given the array [2,3,-2,4],the contiguous subarray [2,3] has the largest product = 6. 这个求最大子数组乘积问题是由最大子数组之和问题演变而来,但是却比求最大子数组之和要复…

the inner product Givens two vectors \(x,y\in \mathbb{R}^n\), the quantity \(x^\top y\), sometimes called the inner product or dot product of the vectors, is a real number given by: \[x^\top y=\begin{bmatrix}x_1 , x_2 ,\cdots ,x_n \end{bmatrix}\begin…

Find the contiguous subarray within an array (containing at least one number) which has the largest product. For example, given the array [2,3,-2,4],the contiguous subarray [2,3] has the largest product = 6. Since two negative numbers may multiply an…

Find the contiguous subarray within an array (containing at least one number) which has the largest product. For example, given the array [2,3,-2,4],the contiguous subarray [2,3] has the largest product = 6. 子数组乘积最大 class Solution { public: int maxPr…