《编程之美》---求二叉树中节点的最大距离

#include <stdio.h>
#include <stdlib.h>

#define A 17
int s[A]={10,6,4,-1,-1,8,-1,-1,14,12,-1,18,-1,-1,16,-1,-1};
int index=0;
int maxlen=0;

typedef struct TREE_NODE
{
	int data;
	struct TREE_NODE* ltree;
	struct TREE_NODE* rtree;
	int lmaxlen;
	int rmaxlen;
}NODE;

NODE* newnode()
{
	NODE* temp;
	temp=(NODE*)malloc(sizeof(NODE));
	return temp;
}

void constructtree(NODE* &pnode)
{
	if(s[index]!=-1)
	{
		pnode=newnode();
		pnode->data=s[index++];
		constructtree(pnode->ltree);
		constructtree(pnode->rtree);
	}
	else
	{
		pnode=NULL;
		index++;
	}
}
/**
	基本思想：

	先序递归，递归到叶子节点后回溯计算
*/
void searchmaxlen(NODE* pnode)
{
	if(pnode->ltree==NULL)
	{
		pnode->lmaxlen=0;
	}
	if(pnode->rmaxlen==NULL)
	{
		pnode->rmaxlen=0;
	}
	if(pnode->ltree!=NULL)
	{
		searchmaxlen(pnode->ltree);
	}
	if(pnode->rtree!=NULL)
	{
		searchmaxlen(pnode->rtree);
	}

	int temp;
	if(pnode->ltree!=NULL)
	{
		if(pnode->ltree->lmaxlen>pnode->ltree->rmaxlen)
		{
			temp=pnode->ltree->lmaxlen;
		}
		else
		{
			temp=pnode->ltree->rmaxlen;
		}
		pnode->lmaxlen=temp+1;
	}
	if(pnode->rtree!=NULL)
	{
		if(pnode->rtree->lmaxlen>pnode->rtree->rmaxlen)
		{
			temp=pnode->rtree->lmaxlen;
		}
		else
		{
			temp=pnode->rtree->rmaxlen;
		}
		pnode->rmaxlen=temp+1;
	}
	if(pnode->lmaxlen+pnode->rmaxlen>maxlen)
	{
		maxlen=pnode->lmaxlen+pnode->rmaxlen;
	}
}

int main(void)
{
	NODE* root;
	constructtree(root);
	searchmaxlen(root);
	printf("The max distance of the tree is %d.\n",maxlen);

	system("pause");
	return 0;
}