Puzzles
Puzzles
Barney lives in country USC (United States of Charzeh). USC has n cities numbered from 1 through n and n - 1 roads between them. Cities and roads of USC form a rooted tree (Barney's not sure why it is rooted). Root of the tree is the city number 1. Thus if one will start his journey from city 1, he can visit any city he wants by following roads.

Some girl has stolen Barney's heart, and Barney wants to find her. He starts looking for in the root of the tree and (since he is Barney Stinson not a random guy), he uses a random DFS to search in the cities. A pseudo code of this algorithm is as follows:
let starting_time be an array of length n
current_time = 0
dfs(v):
current_time = current_time + 1
starting_time[v] = current_time
shuffle children[v] randomly (each permutation with equal possibility)
// children[v] is vector of children cities of city v
for u in children[v]:
dfs(u)
As told before, Barney will start his journey in the root of the tree (equivalent to call dfs(1)).
Now Barney needs to pack a backpack and so he wants to know more about his upcoming journey: for every city i, Barney wants to know the expected value of starting_time[i]. He's a friend of Jon Snow and knows nothing, that's why he asked for your help.
The first line of input contains a single integer n (1 ≤ n ≤ 105) — the number of cities in USC.
The second line contains n - 1 integers p2, p3, ..., pn (1 ≤ pi < i), where pi is the number of the parent city of city number i in the tree, meaning there is a road between cities numbered pi and i in USC.
In the first and only line of output print n numbers, where i-th number is the expected value of starting_time[i].
Your answer for each city will be considered correct if its absolute or relative error does not exceed 10 - 6.
7
1 2 1 1 4 4
1.0 4.0 5.0 3.5 4.5 5.0 5.0
12
1 1 2 2 4 4 3 3 1 10 8
1.0 5.0 5.5 6.5 7.5 8.0 8.0 7.0 7.5 6.5 7.5 8.0
分析:不是太懂,貌似不在当前节点的子树中,却在他父亲的子树中的节点,先比他拜访的概率是0.5;
官方题解:http://codeforces.com/blog/entry/46031
代码:
#include <iostream>
#include <cstdio>
#include <cstdlib>
#include <cmath>
#include <algorithm>
#include <climits>
#include <cstring>
#include <string>
#include <set>
#include <map>
#include <queue>
#include <stack>
#include <vector>
#include <list>
#include <ext/rope>
#define rep(i,m,n) for(i=m;i<=n;i++)
#define rsp(it,s) for(set<int>::iterator it=s.begin();it!=s.end();it++)
#define vi vector<int>
#define pii pair<int,int>
#define mod 1000000007
#define inf 0x3f3f3f3f
#define pb push_back
#define mp make_pair
#define fi first
#define se second
#define ll long long
#define pi acos(-1.0)
const int maxn=1e5+;
const int dis[][]={{,},{-,},{,-},{,}};
using namespace std;
using namespace __gnu_cxx;
ll gcd(ll p,ll q){return q==?p:gcd(q,p%q);}
ll qpow(ll p,ll q){ll f=;while(q){if(q&)f=f*p;p=p*p;q>>=;}return f;}
int n,m,child[maxn],fa[maxn];
double vis[maxn];
vi p[maxn];
int dfs(int now)
{
int cnt=;
for(int x:p[now])cnt+=dfs(x);
return child[now]=cnt+;
}
void work(int now)
{
if(now!=)
vis[now]=vis[fa[now]]++(child[fa[now]]-child[now]-)/2.0;
for(int x:p[now])work(x);
}
int main()
{
int i,j,k,t;
scanf("%d",&n);
rep(i,,n)scanf("%d",&k),p[k].pb(i),fa[i]=k;
vis[]=1.0;
dfs();
work();
rep(i,,n)printf("%g ",vis[i]);
//system ("pause");
return ;
}
Puzzles的更多相关文章
- codeforces A. Puzzles 解题报告
题目链接:http://codeforces.com/problemset/problem/337/A 题意:有n个学生,m块puzzles,选出n块puzzles,但是需要满足这n块puzzles里 ...
- What are the 10 algorithms one must know in order to solve most algorithm challenges/puzzles?
QUESTION : What are the 10 algorithms one must know in order to solve most algorithm challenges/puzz ...
- C puzzles详解
题目:http://www.gowrikumar.com/c/ 参考:http://wangcong.org/blog/archives/291 http://www.cppblog.com/smag ...
- codeforces 377A. Puzzles 水题
A. Puzzles Time Limit: 20 Sec Memory Limit: 256 MB 题目连接 http://codeforces.com/problemset/problem/33 ...
- 【 POJ - 1204 Word Puzzles】(Trie+爆搜|AC自动机)
Word Puzzles Time Limit: 5000MS Memory Limit: 65536K Total Submissions: 10782 Accepted: 4076 Special ...
- 《algorithm puzzles》——谜题
这篇文章开始正式<algorithm puzzles>一书中的解谜之旅了! 狼羊菜过河: 谜题:一个人在河边,带着一匹狼.一只羊.一颗卷心菜.他需要用船将这三样东西运至对岸,然而,这艘船空 ...
- 《algorithm puzzles》——概述
这个专题我们开始对<algorithm puzzles>一书的学习,这本书是一本谜题集,包括一些数学与计算机起源性的古典命题和一些比较新颖的谜题,序章的几句话非常好,在这里做简单的摘录. ...
- [CF697D]Puzzles 树形dp/期望dp
Problem Puzzles 题目大意 给一棵树,dfs时随机等概率选择走子树,求期望时间戳. Solution 一个非常简单的树形dp?期望dp.推导出来转移式就非常简单了. 在经过分析以后,我们 ...
- [cf contest697] D - Puzzles
[cf contest697] D - Puzzles time limit per test 1 second memory limit per test 256 megabytes input s ...
随机推荐
- android 常用
1:常用之动画(View Animation,Drawable Animation,Property Animation) http://blog.csdn.net/huxueyan521/artic ...
- androidstudio--gsonformat--超爽的数据解析方式
很久以前写json解析用原始的解析json的方法,后来为了加快开发进度,开始使用gson,fastjson等第三方jar包来进行json解析,为了保持apk足够小,不因为引入jar包导致apk文件过大 ...
- fragement切换动画效果的实现
标准动画: fragementTransaction.setTransition(FragmentTransation.TRANSIT_FRAGMENT_CLOSE); 自定义动画: fragemen ...
- TD配置安装方式
TD服务器搭建及配置指南 第一:安装前的环境准备 系统需安装IIS作为web服务器(停止IIS的smtp服务). 选择SQL Server2000作为数据库.Win2003需安装SP3. 以管理员登陆 ...
- apache 添加到windows服务
cmd命令行下 输入 “d:\apache\bin\httpd.exe” -k install 如果是resin的话直接运行目录下的setup就可以了, 前提是需要.net framework 3.5
- Eclipse报错 due to restriction on required library C:/Java/jdk1.7.51/jre/lib/rt.jar 解决方案
Eclipse报错 due to restriction on required library C:/Java/jdk1.6.0_10/jre/lib/rt.jar 解决方案 Eclipse 编译时 ...
- PHP编码相关函数试题
1.检查字符串在指定的编码里是否有效的函数是什么? 2.获取字符编码的函数是什么? 3.解析 GET/POST/COOKIE 数据并设置全局变量的函数是什么? 4.大小写不敏感地查找字符串在另一个字符 ...
- vs远程调试
一.远程 建立共享目录debug 二.本地 1.生成->输出->输出路径,由"bin\Debug\"改为远程目录"\\xxx\\debug&quo ...
- curl continue
http://www.cyberciti.biz/faq/curl-command-resume-broken-download/
- byte数组如何转为short数组 (转)
最近在搞毕业设计,做的是有关语音识别的手机应用.在处理音频的过程中,发现需要用short数组处理音频,可能光用byte会越界.但是java读文件没有一次性读到short数组中的api,要么是一个一个读 ...