【HDU - 5883】The Best Path（判断欧拉回路）

题干：

Alice is planning her travel route in a beautiful valley. In this valley, there are NN lakes, and MM rivers linking these lakes. Alice wants to start her trip from one lake, and enjoys the landscape by boat. That means she need to set up a path which go through every river exactly once. In addition, Alice has a specific number (a1,a2,...,ana1,a2,...,an) for each lake. If the path she finds is P0→P1→...→PtP0→P1→...→Pt, the lucky number of this trip would be aP0XORaP1XOR...XORaPtaP0XORaP1XOR...XORaPt. She want to make this number as large as possible. Can you help her?

Input

The first line of input contains an integer tt, the number of test cases. tt test cases follow.

For each test case, in the first line there are two positive integers N (N≤100000)N (N≤100000) and M (M≤500000)M (M≤500000), as described above. The ii-th line of the next NN lines contains an integer ai(∀i,0≤ai≤10000)ai(∀i,0≤ai≤10000) representing the number of the ii-th lake.

The ii-th line of the next MM lines contains two integers uiui and vivi representing the ii-th river between the uiui-th lake and vivi-th lake. It is possible that ui=viui=vi.

Output

For each test cases, output the largest lucky number. If it dose not have any path, output "Impossible".

Sample Input

Sample Output

2
Impossible

题目大意：

一个图，每一条边必须且只能经过一次，写出经过点的路径，类似于p1->p2->p1，求一条路径，使得路径的点的异或和最大，求这个最大值。

解题报告：

首先判断联通，然后看是否有欧拉回路或者欧拉通路，然后两种情况分别判断。如果都没有则输出impossible。

AC代码：

#include<iostream>
#include<cstdio>
#include<cstring>
#include<algorithm>
#include<cmath>
#include<vector>
#include<cctype>
using namespace std;
typedef long long ll;
const int maxn=1e5+10;
int n,m,in[maxn];
int a[maxn];
vector<int> vv[maxn];
int main()
{int t,i,j,k,cnt,u,v,ans=0;int sum=0;cin>>t;    while(t--){scanf("%d%d",&n,&m);cnt=0;for(i=1;i<=n;i++){scanf("%d",&a[i]);in[i]=0;vv[i].clear();}for(i=1;i<=m;i++){scanf("%d%d",&u,&v);vv[u].push_back(v);vv[v].push_back(u);in[u]++; in[v]++;}for(i=1;i<=n;i++){// cout<<i<<":"<<in[i]<<endl;cnt+=(in[i]&1);}if(cnt==1||cnt>2){puts("Impossible");continue;}ans=0;if(cnt){for(i=1;i<=n;i++){if(in[i]&1){ans^=a[i];if(((in[i]-1)/2)%2)ans^=a[i];}else if((in[i]/2)%2)ans^=a[i];}}else {sum=0;for(i=1;i<=n;i++){if((in[i]/2)%2)sum^=a[i];}for(i=1;i<=n;i++)ans=max(ans,sum^a[i]);}printf("%d\n",ans);}return 0;
}

【HDU - 5883】The Best Path（判断欧拉回路）相关推荐

【python初级】os.path.isfile(path)判断路径是否为文件
[python初级]os.path.isfile判断路径是否为文件背景示例背景 os.path.isfile(path)判断路径是否为文件. import os help(os.path.isf ...
hdu 1317 XYZZY【Bellheman_ford 判断正环小应用】
链接: http://acm.hdu.edu.cn/showproblem.php?pid=1317 http://acm.hust.edu.cn/vjudge/contest/view.action ...
HDU 6223 Infinite Fraction Path
链接 http://acm.hdu.edu.cn/showproblem.php?pid=6223 Problem Description The ant Welly now dedicates hi ...
HDU 4850 Wow! Such String! 【欧拉回路】【一顿乱构造】
link: http://acm.hdu.edu.cn/showproblem.php?pid=4850 题解: 每个长度为3的字符串当一个节点,每个节点连出26条边,代表给长度为3的字符串吼添加'a ...
hdu 4725 The Shortest Path in Nya Graph（建图+优先队列dijstra）
题目链接:http://acm.hdu.edu.cn/showproblem.php?pid=4725 题意:有n个点和n层,m条边,每一层的任意一个点都可以花费固定的值到下一层或者上一层的任意点然 ...
HDU 1269 迷宫城堡 -- 强连通图判断
题目地址:http://acm.hdu.edu.cn/showproblem.php?pid=1269 图的强连通分量 http://baike.baidu.com/link?url=NqsmNsGC ...
HDU - 4725 The Shortest Path in Nya Graph(最短路+思维)
题目链接:点击查看题目大意:给定n个点,在一般的基础上给每个点一个维度,也就是多了一个参数表示所在的层次,现在已知: X层的点可以通过增加权值C到达X-1层或X+1层中的任何一个点给定m个已经形成 ...
HDU 2224 The shortest path
传送门属于动态规划.TSP(旅行商)问题的简化版本,双调旅行商问题.时间复杂度O(n^2). 可以参考这个. 给你平面上n个点的坐标,这些点的x坐标依次增大,让你找一条满足这样的性质的最短的路:从1 ...
hdu 3600 Simple Puzzle （判断N 数码是否有解）
分析: 当N为奇数时奇偶同性可互达,N为偶数时,逆序数之和sum加上空格所在行距目标空格行的距离dis之和要和终点状态逆序数同奇偶 View Code #include<iostream> ...

【HDU - 5883】The Best Path（判断欧拉回路）

【HDU - 5883】The Best Path（判断欧拉回路）相关推荐

最新文章

热门文章