hdu 3999 The order of a Tree

#include <iostream>#include <stdlib.h>using namespace std;int flag;typedef struct BSTNode{int value;struct BSTNode *left,*right;}BSTNode,*BSTree;void CreatTree(BSTree &T,int temp)///Creat的时候一定是&BiTree{if(T==NULL){   T=(BSTree)malloc(sizeof(BSTNode));        T->value=temp;        T->left=T->right=NULL;}else if(temp<T->value)CreatTree(T->left,temp);else CreatTree(T->right,temp);}void PreBSTree(BSTree T){if(T!=NULL){      if(flag==0)      {       cout<<T->value;       flag=1;       }       else cout<<" "<<T->value;   PreBSTree(T->left);   PreBSTree(T->right);     }}int main(){    int n,x;    while(cin>>n)    {    BSTree root=NULL;    for(int i=0;i<n;i++)    {    cin>>x;    CreatTree(root,x);    }    flag=0;    PreBSTree(root);    cout<<endl;    }return 0;}

二叉搜索树建树，然后先序输出。