今晚搞清楚了二叉树的建立和先序遍历，不过现在已经是0:32了，该睡觉了，贴上代码，明天补充细节，加油，晚安！

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#include<iostream>
#include <malloc.h>
#include<stdio.h>
using namespace std;
struct node
{
    int data;
    struct node* left;
    struct node* right;
};
void visit(node* BT);
node* creat();
node* creat(node* &T);
void preOrder(node*T);
int main()
{
    node* BT;
    BT=creat();
    preOrder(BT);
    return 0;
}
void visit(node* BT)
{
    cout<<BT->data<<' ';
    //cout<<"hi"<<endl;
}
node* creat()
{
    node* T;
    int num;
    scanf("%d",&num);
    if(num=='0')
        T=NULL;
    else
    {
        T = (node*)malloc(sizeof(node));
        T->data = num;
        //cout<<num;
        T->left = creat();
        T->right = creat();

    }
    return T;

}
void preOrder(node*T)
{
    if(T==NULL)
        return;
    else
    {
        visit(T);
        preOrder(T->left);
        preOrder(T->right);     
    } 
}