hdu1305 Immediate Decodability (字典树)

题目连接：http://acm.hdu.edu.cn/showproblem.php?pid=1305

题解：判断字符串是否存在前缀

#include <stdio.h>  
#include <string.h>  
#define MAXN 100002  

int child[MAXN][11];//child[i][j]=0说明没有对应的节点,以i为根节点的子树,  
int flag[MAXN]; 
int tot,root;  

void Trie()  
{  
	memset(child[0],0,sizeof(child[0]));  
	flag[0]=0;  
	tot=root=0;//根节点为0  
}  

int inset(char *str)  
{  
	int *cur=&root,ans=0;  
	char *ptr;  
	for(ptr=str;*ptr;++ptr)  
	{  
		cur=&child[*cur][*ptr-'0'];  
		if(*cur==0)  
		{  
			*cur=++tot;  
			ans=1;  
			memset(child[tot],0,sizeof(child[tot]));  
			flag[tot]=0;  
		}  
		if(flag[*cur]==1)  
			return 0;  
	}  
	flag[*cur]=1;  
	return ans;  
}  


int main()  
{  
	char str[12];  
	int ans,test=1;  
	while(scanf("%s",str)!=EOF)  
	{  
		Trie();  
		ans=1;  
		if(!inset(str))
			ans=0;
		while(scanf("%s",str)&&strcmp(str,"9")!=0)
		{
			if(ans)
			{
				if(!inset(str))
					ans=0;
			}
		}
		if(ans)
			printf("Set %d is immediately decodable\n",test++);
		else
			printf("Set %d is not immediately decodable\n",test++);
	}  
	return 0;  
}