二叉搜索树

#include <iostream>
#include <cstdio>
#include <cstring>
#define maxn 1000
#define T char
using namespace std;
typedef struct btnode{
    T data;
    struct btnode *lchild;
    struct btnode *rchild;
}btnode;
btnode *root = NULL;

btnode* newnode(T x) {
    btnode* p = (btnode* )malloc(sizeof(btnode));
    p->data = x;
    p->lchild = NULL;
    p->rchild = NULL;
    return p;
}

bool insert1(T x){
    btnode *r = NULL, *q = NULL, *p = root;
    T k = x;
    while(p) {
        q = p;
        if(k < p->data) {
            p = p->lchild;
        }
        else if(k > p->data) {
            p = p->rchild;
        }
        else {
            cout << "duplicate!" << endl;
            return false;
        }
    }
    r = newnode(x);
    if(root) {
        if(k < q->data) {
            q->lchild = r;
        }
        else {
            q->rchild = r;
        }
    }
    else{
        root = r;
    }
    return true;
}

void preorder(btnode *bt) {
    if(bt) {
        preorder(bt->lchild);
        cout << bt->data << ' ';
        preorder(bt->rchild);
    }
    if(bt == NULL) {
        return ;
    }
}


int main()
{
    char str[maxn];
    int len = 0;
    gets(str);
    len = strlen(str);
    for(int i = 0; i < len; i++) {
        insert1(str[i]);
    }
    btnode *temp = root;
    preorder(temp);
    return 0;
}