#include <iostream>
#include <cstdlib>
#include <string.h>
#include <algorithm>
#define ss(a)  scanf("%d",&a)
#define ss64(a)  scanf("%I64d",&a)
using namespace std;

typedef struct Node
{
    struct Node *l;
	struct Node *r;
	int num;
}*node;

void creat(node &T,int num)             //此处的&的引用是关键
{
   if (T == NULL)
   {
       T = (node)malloc(sizeof(Node));
	   T->num = num;
	   T->l = NULL;
	   T->r = NULL;;
   }
   else
	   if (num < T->num)
	   {
		   creat(T->l,num);
	   }
	   else
	   {
		   creat(T->r,num);
	   }
   
}


void post_visit(node T,int x)
{
    if (T != NULL)
    {
		if(x)
		   cout<<T->num;
		else
		   cout<<" "<<T->num;
		post_visit(T->l,0);
		post_visit(T->r,0);
    }
}

int main()
{
	int i,n,m,sum,cnt,j;
	int num;
	node T=NULL;
	while(~ss(n))
	{
		for (i=0;i<n;i++)
        {
			 ss(num);
			 creat(T,num);
		}
        post_visit(T,1);  
		cout<<endl;
	}
    return 0;
}

考察二叉树的创建以及先序遍历

The order of a Tree

4

1 3 4 2

1 3 2 4

HDU 3999 The order of a Tree 二叉树

原文：http://blog.csdn.net/xinwen1995/article/details/45722299