基本二叉搜索树的第K小元素

#include<stdio.h>
#include<stdlib.h>
typedef struct node *btlink;
struct node
{
    int data;
    btlink left;
    btlink right;
    int t;
};

btlink BT;
void insert(btlink q, int x)
{  
    btlink p = (btlink)malloc(sizeof(node)); 
    p->data = x; 
    p->left = NULL; 
    p->right = NULL;
    p->t=0;
    if(q == NULL)
    {    
        BT = p; 
        //printf("BT=%d\n",BT->t);
        return ; 
    }       
    while(q->left!=p&&q->right!=p)
    {       
        if(x<q->data)
        {     
            if(q->left)
            {    
                q->t++;
                q = q->left;
            }  
            else
            {  
                q->t++;
                q->left = p; 
            }         
        }        
        else
        {   
            if(q->right)
            {     
                q = q->right; 
            }     
            else
            {   
                q->right = p; 
            }  
        }    
    }   
    return;
}
void InOrder(btlink root,int k)
{
    
    while(k!=root->t+1)
    {
        //printf("k=%d t=%d\n",k,root->t);
        if(k>root->t+1)
        {
            k=k-root->t-1;
            root=root->right;
        }
        else
        {
            
            root=root->left;
        }
    }
    printf("%d\n",root->data);
}

int main()
{
    int n,i,index=0,x;
    char a[8];
    scanf("%d",&n);
    BT=(btlink)malloc(sizeof(node));
    BT=NULL;
    for(i=0;i<n;i++)
    {
        scanf("%s",a);
        if(a[0]=='a')
        {
            scanf("%d",&x);
            insert(BT,x);
        }
        else if(a[0]=='p')
        {
            
            index++;
            InOrder(BT,index);
        }
    }
    return 0;
}