hdu 3999(二叉排序树)

#include<iostream>
using namespace std;
bool first;

struct BST{
int data;
BST *leftchild;
BST *rightchild;
};

void Build(BST *&root,int x){
if(root==NULL){
root=(BST *)malloc(sizeof(BST));
root->data=x;
root->leftchild=root->rightchild=NULL;
}else {
if(x<root->data){
Build(root->leftchild,x);
}else
Build(root->rightchild,x);
}
}

void Search(BST *root){
if(root!=NULL&&first){
first=false;
printf("%d",root->data);
Search(root->leftchild);
Search(root->rightchild);
}else if(root!=NULL){
printf(" %d",root->data);
Search(root->leftchild);
Search(root->rightchild);
}
}

int main(){
int n;
while(~scanf("%d",&n)){
BST *root=NULL;
first=true;
for(int i=1;i<=n;i++){
int x;
scanf("%d",&x);
Build(root,x);
}
Search(root);
printf("\n");
}
return 0;
}