hdu 1251 字典树 求前缀有多少个

做的第一个字典树，非常直观

第一类是求前缀有多少个，第二类是求前缀是否在一串字符中出现

主要是字典树的构造，使用了一个嵌套的结构体，使用了指针，非常方便

也非常巧妙，还有就是root，newnode必须初始空间

banana
band
bee
absolute
acm

ba
b
band
abc

#include <stdio.h>
#include <string.h>
#include <malloc.h>

struct dictree
{
	dictree *child[26];
	int n;
};

struct dictree *root;

void insert(char *str)
{
	struct dictree *current,*newnode;

	int len=strlen(str);

	current=root;

	for(int i=0;i<len;i++)
	{
		if(current->child[str[i]-'a']!=0)
		{
			current=current->child[str[i]-'a'];
			current->n=current->n+1;
		}else
		{
			newnode=(struct dictree*)malloc(sizeof(struct dictree));

			for(int j=0;j<26;j++)
				newnode->child[j]=0;
			current->child[str[i]-'a']=newnode;
			current=newnode;
			current->n=1;
		}
	}
}

int find(char *str)
{
	struct dictree *current;

	int len=strlen(str);

	int i;

	if(len==0)return 0;

	current=root;

	for(i=0;i<len;i++)
	{
		if(current->child[str[i]-'a']!=0)
			current=current->child[str[i]-'a'];
		else
			return 0;
	}

	return current->n;
}

int main()
{
	char strs[11];

	int i;

	root=(struct dictree*)malloc(sizeof(struct dictree));

	for(i=0;i<26;i++)
		root->child[i]=0;

	root->n=2;

	while(gets(strs),strcmp(strs,"")!=0)
		insert(strs);	
	
	while(scanf("%s",strs)!=EOF)
	{
		printf("%d\n",find(strs));
	}

	return 0;
}