poj2337 Catenyms

第一次写欧拉路，有点郁闷，不过知道了，欧拉的判定是否可以用并查集哦，这题是纯模板的

#include"stdio.h"
#include"math.h"
#include"string.h"
#include"stdlib.h"

typedef struct node
{
	int from,to,vis;
	
}Node;
Node map[1001];
char str[1001][21],str1[1001][21];
int po[27];
int m,n,e;

int cmp(const void *a,const void *b)
{
	return strcmp((char *)a,(char *)b);
}

int find(int x)
{
	int i,j;
	i = x;
	while(x!=po[x])x = po[x];
	
	while(i!=x)
	{
		j     = po[i];
		po[i] = x;
		i     = j;
	}
	return x;
}

void eurlar(int u)
{
	int i;
	
	for(i=1;i<=e;i++)
	{
		if(!map[i].vis && map[i].from==u)
		{
			map[i].vis = 1;
			eurlar(map[i].to);
			strcpy(str1[++n],str[i]);
		}
	}
}

int main()
{
	int text,i,j,k,len,a,b,a1,a2,in[27],out[27],us[27];
	
	scanf("%d",&text);
	while(text--)
	{
		scanf("%d",&e);
		if(e<3){printf("***");printf("\n");continue;}
		for(i=1;i<=26;i++)po[i] = i;
		for(i=1;i<=26;i++)in[i] = out[i] = us[i] = 0;
		for(i=1;i<=e;i++)
		{
			scanf("%s",str[i]);
		}
		qsort(str+1,e,sizeof(str[0]),cmp);
		//for(i=1;i<=e;i++)printf("%d %s\n",i,str[i]);
		for(i=1;i<=e;i++)
		{
			len = strlen(str[i]);
			a = str[i][0]-'a'+1;
			b = str[i][len-1]-'a'+1;//printf("a = %d b = %d \n",a,b);
			a1= find(a);//并查集
			a2= find(b);
			po[a1] = a2;
			map[i].from = a;
			map[i].to   = b;
			map[i].vis  = 0;
			us[a]       = 1;
			us[b]	    = 1;		    
			out[a]++;
			in[b]++;
		}
		a = b = 0;
		for(i=1;i<=26;i++)//是不是在一棵树内
		{//printf("i = %d  po[] = %d us= %d\n",i,po[i],us[i]);
			if(i==po[i] && us[i])b++;
		}//printf("b = %d\n",b);
		if(b>1)
		{
			printf("***");
			printf("\n");
			continue;
		}
		a = b = 0;
		for(i=1;i<=26;i++)//入度和出度是否相等，且至多有一对差1
		{
			if(in[i]==out[i])continue;//{printf("in=%d,out=%d\n",in[i],out[i]);continue;}
			else if(in[i]-1==out[i])a++;
			else if(in[i]+1==out[i])b++;
			else break;
		}//printf("i =%d,a=%d,b=%d\n",i,a,b);
		if(i<=26 || a!=b || a>1 || b>1)
		{
			printf("***\n");
			continue;
		}
		n = 0;
		a1 = 1;
		
		if(a==1)//这是很严重的问题，当是欧拉路对时候，要找到原点，不然结果只是wa
		{
			for(i=1;i<=e;i++)
			{
				if(out[map[i].from]-in[map[i].from]==1)//找到起点
				{
					a1 = i;
					break;
				}
			}
		}
		eurlar(map[a1].from);
		for(i=n;i>=1;i--)
		{
			printf("%s",str1[i]);
			if(i>1)printf(".");
		}
		printf("\n");
	}
	return 0;
}