Leader in Tree Land Time Limit: 2000/1000 MS (Java/Others)    Memory Limit: 65536/65536 K (Java/Others)Total Submission(s): 447    Accepted Submission(s): 185 Problem DescriptionTree land has n cities, connected by n−1 roads. You can go to any city f…

题目链接:http://acm.hdu.edu.cn/showproblem.php?pid=5378 题意:一棵n个节点的树.对其节点进行标号(1~n).求恰好存在k个节点的标号是其节点所在子树的最大值的方案数. 解法: 首先,总共有n!中标号方案.而如果求出n个节点中出现k个上述节点的概率p.方案数等于n!* p. dp[i][j] 表示钱i个节点有j个上述节点的概率.转移较容易推出. dp[i][j] = dp[i-1][j] * (c[i]-1) / c[i] + dp[i-1][j-1…

题意: 给你一颗以1位根节点的树.我们定义对于每一个子树,节点权值最大的权值记为这个子树的权值,为你将1~n放到这个树里 满足最大权值仅仅有k个的组合数是多少. 思路: 我们能够知道以每一个节点为子树.且根节点权值最大的概率是多少,不是的概率是多少. 那么事实上问题就变成了 我们在n个物品里面,每一个物品拿的概率是pi不拿的概率是1-pi 问你拿k个物品的概率是多少 然后最后乘n!就好了.中间计算运用逆元. 代码: #include"cstdlib" #include"cst…

tree Time Limit: 8000ms Memory Limit: 262144KB This problem will be judged on HDU. Original ID: 539064-bit integer IO format: %I64d      Java class name: Main   Given a rooted tree(node 1 is the root) with n nodes. The ithnode has a positive value vi…

Yu-Gi-Oh! Time Limit: 2000ms Memory Limit: 65536KB This problem will be judged on HDU. Original ID: 538364-bit integer IO format: %I64d      Java class name: Main   "Yu-Gi-Oh!", also known as "Dueling Monsters", is a popular trading ca…

The path Time Limit: 2000ms Memory Limit: 65536KB This problem will be judged on HDU. Original ID: 538564-bit integer IO format: %I64d      Java class name: Main Special Judge   You have a connected directed graph.Let d(x) be the length of the shorte…

Boring Class Time Limit: 6000/3000 MS (Java/Others)    Memory Limit: 65536/65536 K (Java/Others)Total Submission(s): 900    Accepted Submission(s): 247 Problem Description Mr. Zstu and Mr. Hdu are taking a boring class , Mr. Zstu comes up with a prob…

RGCDQ Time Limit: 6000/3000 MS (Java/Others)    Memory Limit: 65536/65536 K (Java/Others)Total Submission(s): 1652    Accepted Submission(s): 696 Problem Description Mr. Hdu is interested in Greatest Common Divisor (GCD). He wants to find more and mo…

CRB and Apple Time Limit: 12000/6000 MS (Java/Others)    Memory Limit: 65536/65536 K (Java/Others)Total Submission(s): 421    Accepted Submission(s): 131 Problem Description In Codeland there are many apple trees.One day CRB and his girlfriend decide…

CRB and Queries Time Limit: 12000/6000 MS (Java/Others)    Memory Limit: 131072/131072 K (Java/Others)Total Submission(s): 533    Accepted Submission(s): 125 Problem DescriptionThere are N boys in CodeLand.Boy i has his coding skill Ai.CRB wants to k…