poj 2513 Colored Sticks(并查集+hash+欧拉图)

Colored Sticks Time Limit: 5000MS   Memory Limit: 128000K Total Submissions: 39375   Accepted: 10265 Description You are given a bunch of wooden sticks. Each endpoint of each stick is colored with some color. Is it possible to align the sticks in a straight line such that the colors of the endpoints that touch are of the same color? Input Input is a sequence of lines, each line contains two words, separated by spaces, giving the colors of the endpoints of one stick. A word is a sequence of lowercase letters no longer than 10 characters. There is no more than 250000 sticks. Output If the sticks can be aligned in the desired way, output a single line saying Possible, otherwise output Impossible. Sample Input blue red red violet cyan blue blue magenta magenta cyan Sample Output Possible Hint Huge input,scanf is recommended. Source The UofA Local 2000.10.14

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标准做法是用并查集+欧拉图+字典树，但是我不想敲字典树

先用了map，毫无意外tle了，然后就想用hash试一下，然后直接过了。。。(不知道那些用map过的到底怎么写的。。。)

个人觉得unordered_map应该也能过，可惜poj貌似不能用c++11

其实这题最坑的地方是有空输入，这个时候输出possible

#include <iostream>
#include <cstdio>
#include <algorithm>
#include <map>

using namespace std;
const int maxn = 250010*2;

int  sett[maxn];
int used[maxn];


unsigned int hasha(char *url)
{
	unsigned int nn=0;
	char *b=(char *)&nn;
	for(int i=0;url[i];++i)
		b[i%4]^=url[i];
	return nn%maxn;
}

int findSet(int x)
{
    if(x==sett[x])
        return x;
    int y = findSet(sett[x]);
    return sett[x] = y;
}

void unionSet(int x,int y)
{
    int x1 = findSet(x);
    int y1 = findSet(y);
    if(x1!=y1)
    {
        sett[x1] = y1;
    }
}
char str1[15],str2[15];
int ma[maxn];
int main()
{
    int t =0,flag =1;
    for(int i = 0;i<=maxn;i++)
        {
            sett[i] = i;
            used[i] = 0;
        }
    //map<string,int> ma;
    while(scanf("%s%s",str1,str2)!=EOF)
    {
        unsigned int s1 = hasha(str1);
        unsigned int s2 = hasha(str2);
        if(ma[s1]==0)
        ma[s1] = t++;
        if(ma[s2]==0)
        ma[s2] = t++;
        used[ma[s1]]++;
        used[ma[s2]]++;
        unionSet(ma[s1],ma[s2]);
    }
    int k = 0;
    int m = 0;
    for(int i =0;i<t-1;i++)
    {
        if(sett[i] == i)
            {
                m++;
                //cout<<i<<endl;
            }
        if(used[i]%2==1)
            k++;
    }
    //cout<<m<<endl;
    if((k!=0&&k!=2)||m!=1)
        flag = 0;
    if(t==0)
        flag = 1;
    //cout<<flag<<endl;
    if(flag)
      cout<<"Possible"<<endl;
    else
      cout<<"Impossible"<<endl;
}