Hdu 3999 - The order of a Tree

#include <stdio.h>
#include <string.h>
#include <algorithm>
using namespace std;
int p[100100],i=0;
struct node
{
int data;
node *lson,*rson;
};
node *T;
int cnt=0;
node temp[100100];
node *newNode(int val)
{
node *T=temp+cnt;
cnt++;
T->lson=NULL;
T->rson=NULL;
T->data=val;
return T;
}
node *Insert(int val,node *T)
{
if(T==NULL)
T=newNode(val);
else
{
if(val<T->data)
{
if(T->lson==NULL)
T->lson=newNode(val);
else
Insert(val,T->lson);
}
else
{
if(T->rson==NULL)
T->rson=newNode(val);
else
Insert(val,T->rson);
}
}
return T;
}
void preOrder(node *T)
{
if(T==NULL)
return;
p[i]=T->data;
i++;
preOrder(T->lson);
preOrder(T->rson);
}
int main()
{
long n,i;
int k[100100];
while(scanf("%ld",&n)!=EOF)
{
for(i=0;i<n;i++)
scanf("%d",&k[i]);
cnt=0;
for(i=0;i<n;i++)
T=Insert(k[i],T);
preOrder(T);
for(i=0;i<n;i++)
{
printf("%d",p[i]);
if(i<n-1)
printf(" ");
}
printf("\n");
}
return 0;
}