二叉排序树

题目：https://www.nowcoder.com/practice/b42cfd38923c4b72bde19b795e78bcb3?tpId=40&tqId=21555&tPage=2&rp=2&ru=/ta/kaoyan&qru=/ta/kaoyan/question-ranking

第十二行一开始没写搞得一直报错。

代码

#include <cstdio>
#include <vector>
using namespace std;
struct Node{
    int data;
    Node* lchild;
    Node* rchild;
};
void insert(Node* &root, int input){
    if(root == NULL){
        root = new Node;
        root->data = input;
        root->lchild = NULL;
        root->rchild = NULL;
        return;
    }
    if(input == root->data) return;
    else if(input > root->data){
        insert(root->rchild, input);
    }
    else {
        insert(root->lchild, input);
    }
    return;
}
void pre_order(Node *root){
    if(root == NULL) return;
    printf("%d ",root->data);
    pre_order(root->lchild);
    pre_order(root->rchild);
}
void in_order(Node *root){
    if(root == NULL) return;
    in_order(root->lchild);
    printf("%d ",root->data);
    in_order(root->rchild);
}
void post_order(Node *root){
    if(root == NULL) return;
    post_order(root->lchild);
    post_order(root->rchild);
    printf("%d ",root->data);
}
int main(){
    int n, input;
    while(scanf("%d", &n)!=EOF){
        Node *root = NULL;
        vector<int> input(n, 0);
        for(int i = 0; i < n; i++) scanf("%d", &input[i]);
        for(int i = 0; i < n; i++){
            insert(root, input[i]);
        }
        pre_order(root);
        printf("\n");
        in_order(root);
        printf("\n");
        post_order(root);
        printf("\n");
    }
    return 0;
}