[HDU 5293]Tree chain problem(树形dp+树链剖分) 题面 在一棵树中,给出若干条链和链的权值,求选取不相交的链使得权值和最大. 分析 考虑树形dp,dp[x]表示以x为子树的最大权值和(选的链都在i的子树中) 设sum[x]表示x的儿子的dp值和,即\(\sum _{y \in \mathrm{son}(x)} dp[y]\) 1.不选两端点lca为x的链,dp[x]=sum[x] 2.选两端点lca为x的链,则dp[x]=max{链的权值+链上节点的所有子节点dp的…

题目链接:http://lightoj.com/login_main.php?url=volume_showproblem.php?problem=1004 题意:数塔的变形,上面一个下面一个,看清楚了直接做就行了. 上半部分转移方程dp(i,j)=max(dp(i-1,j),dp(i-1,j+1))+G(i,j) 下半部分转移方程dp(i,j)=max(dp(i-1,j-1),dp(i-1,j))+G(i,j) #include <algorithm> #include <iostre…

Hard problem 题目链接: http://codeforces.com/contest/706/problem/C Description Vasiliy is fond of solving different tasks. Today he found one he wasn't able to solve himself, so he asks you to help. Vasiliy is given n strings consisting of lowercase Engl…

You are in the world of mathematics to solve the great "Monkey Banana Problem". It states that, a monkey enters into a diamond shaped two dimensional array and can jump in any of the adjacent cells down from its current position (see figure). Wh…

A Scheduling Problem   Description There is a set of jobs, say x1, x2,..., xn <tex2html_verbatim_mark>, to be scheduled. Each job needs one day to complete. Your task is to schedule the jobs so that they can be nished in a minimum number of days. Th…

dp(i, j)表示从i~N中为j个人选定的方案数, 状态转移就考虑选多少人为i编号, 然后从i+1的方案数算过来就可以了. 时间复杂度O(TN^2) --------------------------------------------------------------------- #include<cstdio> #include<algorithm> #include<cstring>   using namespace std;   typedef lon…

概率dp... http://blog.csdn.net/Vmurder/article/details/46467899 ( from : [辗转山河弋流歌 by 空灰冰魂] ) 这个讲得很好 , 推推公式就可以 O( n ) , 但是 n 最大是99999999 , 怎么破....其实 n 很大时概率基本不动了...所以只需计算到某一个较大值时就可以停下来了... ----------------------------------------------------------------…

题目链接:hdu 5106 Bits Problem 题目大意:给定n和r,要求算出[0,r)之间全部n-onebit数的和. 解题思路:数位dp,一个ct表示个数,dp表示和,然后就剩下普通的数位dp了.只是貌似正解是o(n)的算法.可是n才 1000.用o(n^2)的复杂度也是够的. #include <cstdio> #include <cstring> #include <algorithm> using namespace std; typedef long…

题目链接:http://hihocoder.com/problemset/problem/1259 题目大意:g(t)=(f(i)%k=t)的f(i)的个数 求所有的(0-k-1)的g(i)的异或总值 思路:首先推出公式3*f(n)*f(2n+1)=f(2n)*(1+3f(n)) 3f(n)和3f(n)+1相邻的两个数肯定是互质的 所以解出f(2n)=3*f(n) f(2n+1)=3*f(n)+1 相当于是n表示成2进制但是每位的权值为3 然后就是数位dp的过程了 dp[k][i][j] k表示…

2302: [HAOI2011]Problem c Time Limit: 30 Sec  Memory Limit: 256 MBSubmit: 648  Solved: 355[Submit][Status][Discuss] Description 给n个人安排座位,先给每个人一个1~n的编号,设第i个人的编号为ai(不同人的编号可以相同),接着从第一个人开始,大家依次入座,第i个人来了以后尝试坐到ai,如果ai被占据了,就尝试ai+1,ai+1也被占据了的话就尝试ai+2,……,如果一直…