自己试了几组数据没发现问题，上传以后只有两个AC，其他是WA，求大佬帮我看下是那里的问题

#include <stdio.h>
#include <stdlib.h>

struct node{
	char data;
	struct node* left;
	struct node* right;
};

struct node* root=0;

void insert (char x[]);
struct node* newnode (char x);
void preorder (struct node* r);
void pre (struct node* r,char x[]);

int main()
{
	int n=0;
	int i=0;
	char x[3];
	
	scanf("%d",&n);
	
	for(i=0;i<n;i++){
		scanf("%s",x);
		insert(x);
	}
	
	preorder(root);
	
	return 0;
}

void insert (char x[])
{
	struct node* r=0;
	r=root;
	
	if(r==0){
		root=newnode(x[0]);
		root->left=newnode(x[1]);
		root->right=newnode(x[2]);
	}else{
		pre(root,x);
	}
	
}

struct node* newnode (char x)
{
	struct node* t=(struct node*)malloc(sizeof(struct node));
	
	if(x=='*'){
		return 0;
	}
	
	t->data=x;
	t->left=0;
	t->right=0;
	
	return t;
}

void preorder (struct node* r)
{
	if(r==0){
		return;
	}
	
	printf("%c",r->data);
	preorder(r->left);
	preorder(r->right);
}

void pre (struct node* r,char x[])
{
	if(r==0){
		return;
	}
	
	if(r->data==x[0]){
		r->left=newnode(x[1]);
		r->right=newnode(x[2]);
		return;
	}
	
	pre(r->left,x);
	pre(r->right,x);
}