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]);elsecontinue;}read(&root);