Operation on character string to delete same alphabet

#include<stdio.h>
#include<stdlib.h>
char a[]={'a','b','a','c','a','c','d','e','k','b'};
typedef char key_type;
typedef struct node{
	key_type key;
	struct node *next;
}node, *pnode;

void insert(pnode *root, key_type key)
{
	pnode p = (pnode)malloc(sizeof(node));
	pnode temp;
	p->key = key;
	p->next = NULL;

	if( (*root) == NULL)
	{
		( *root ) = p;
		return ;
	}
	insert(&(*root)->next,key);
}
int find(pnode root, key_type key)
{
	pnode temp;
	if( root ==NULL )
		return 0;

	while( root && key != root->key)
	{
		root =root->next;
	}
	if( root == NULL)
		return 0;
	if( key == root->key)
		return 1 ;

}
void read(pnode *root )
{
	pnode temp =(*root);
	while(temp)
	{
		printf("%c ",temp->key);
		temp = temp->next;
	}
}
void main()
{
	int i;
	pnode root = NULL ;
	for(i=0;i<10;i++)
	{
		if( find( root , a[i] ) == 0 )
			insert(&root,a[i]);
		else
			continue;
	}
	read(&root);