A - Colored Sticks
Time Limit:5000MS Memory Limit:128000KB 64bit IO Format:%I64d & %I64u
Submit Status
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.
使用字典树来给每个颜色定一个序号，并统计出现的次数，使用并查集判断是否全部的点联通，在用欧拉回路，看整个图是不是可以一次走完，
判断方法，如果奇数度数的点为0或2个，那么一定可以走通
#include <cstdio>
#include <cstring>
int p[520000] , top , q[520000];
struct node{
int flag ;
node *next[27] ;
} *head;
node *newnode()
{
node *p = new node ;
p->flag = 0;
for(int i = 0 ; i < 27 ; i++)
p->next[i] = NULL ;
return p;
}
int gettree(node *head,char *s)
{
int i , l = strlen(s) ;
node *p = head ;
for(i = 0 ; i < l ; i++)
{
int k = s[i] - 'a' ;
if(p->next[k]==NULL)
p->next[k] = newnode();
p = p->next[k] ;
}
if( p->flag == 0 )
p->flag = top++ ;
return p->flag ;
}
int f(int x)
{
int r , k , l ;
r = x ;
while( r != p[r] )
r = p[r] ;
k = x ;
while( k != r )
{
l = p[k] ;
p[k] = r ;
k = l ;
}
return r ;
}
void add(int u,int v)
{
u = f(u) ;
v = f(v) ;
if( u != v )
p[u] = v ;
}
char s1[11] , s2[11] ;
int main()
{
int i , n , k1 , k2 ;
memset(q,0,sizeof(q));
head = newnode() ;
for(i = 0 ; i <= 520000 ; i++)
p[i] = i ;
top = 1 ;
while( scanf("%s %s", s1, s2 ) !=EOF )
{
k1 = gettree(head,s1);
k2 = gettree(head,s2);
q[k1]++ ;
q[k2]++ ;
add(k1,k2) ;
}
int k = f(1) ;
for(i = 2 ; i < top ; i++)
if( k != f(i) )
break;
if( i < top )
printf("Impossible\n");
else
{
int ji = 0 ;
for(i = 1 ; i < top ; i++)
if( q[i]%2 )
ji++ ;
if(ji ==0 || ji == 2)
printf("Possible\n");
else
printf("Impossible\n");
}
return 0;
}
测试赛A - Colored Sticks（并查集+字典树+欧拉回路）