输入前序遍历和中序遍历输出后序遍历——在构树和不构树两种情况下输出结果

#include<iostream>
using namespace std;


struct BinaryTreeNode
{
int m_nvalue;
BinaryTreeNode *m_pLeft;
BinaryTreeNode *m_pRigt;
};


BinaryTreeNode* ConstructCore(int *startpreorder, int *endpreorder, int *startinorder, int *endinorder)
{
//if (startpreorder == endpreorder)
//return startpreorder;


BinaryTreeNode *p = new BinaryTreeNode;
p->m_nvalue = startpreorder[0];
p->m_pLeft = NULL;
p->m_pRigt = NULL;
if (startpreorder == endpreorder)
return p;


int i = 0;
while (1)
{
if (startpreorder[0] == startinorder[i])
break;
else
++i;
/*if (i >= endpreorder - startpreorder + 1)
{
cout << "输入错误无法建立二叉树！" << endl;
return NULL;
}*/
}
if (i > 0)
p->m_pLeft = ConstructCore(startpreorder + 1, startpreorder + i, startinorder, startinorder + i-1);


if (i < endpreorder - startpreorder)
p->m_pRigt = ConstructCore(startpreorder + i + 1, endpreorder, startinorder + i + 1, endinorder);


return p;






}




BinaryTreeNode* Construct(int *preorder, int *inorder, int length)
{
if (preorder == NULL || inorder == NULL || length <= 0)
return NULL;
return ConstructCore(preorder, preorder + length - 1, inorder, inorder + length - 1);
}


//后序遍历打印二叉树
void LastCout(BinaryTreeNode *root)
{
if (root == NULL)
return;
LastCout(root->m_pLeft);
LastCout(root->m_pRigt);
cout << root->m_nvalue << " ";
}




void ACore(int *startpreorder, int *endpreorder, int *startinorder, int *endinorder)
{

if (startpreorder == endpreorder)
{
cout << startinorder[0] << " ";
return;
}



int i = 0;
while (1)
{
if (startpreorder[0] == startinorder[i])
break;
else
++i;
}
if (i > 0)
ACore(startpreorder + 1, startpreorder + i, startinorder, startinorder + i - 1);


if (i < endpreorder - startpreorder)
ACore(startpreorder + i + 1, endpreorder, startinorder + i + 1, endinorder);


cout << startpreorder[0] << " ";
}


// 输入前序遍历和中序遍历 输出后序遍历（前提 数组中数不能相等）
void A(int *preorder, int *inorder, int length)
{
if (preorder == NULL || inorder == NULL || length <= 0)
return;
else
ACore(preorder, preorder + length - 1, inorder, inorder + length - 1);
}


int main()
{
int preorder[] = { 1, 2, 4, 5, 6, 7, 3 };
int inorder[] = { 4, 2, 6, 5, 7, 1, 3 };
const int length = sizeof(preorder) / sizeof(preorder[0]);


BinaryTreeNode *p = Construct(preorder, inorder, length);  //先构树 再输出后序遍历
LastCout(p);
cout << endl;
A(preorder, inorder, length); //直接输出后序遍历
cout << endl;


return 0;




}