剑指offer编程题——06 重建二叉树

#include<iostream>
using namespace std;
struct BinaryTreeNode{
int m_value;
BinaryTreeNode* m_left;
BinaryTreeNode* m_right;
};
BinaryTreeNode* ConstructCore(int* startPre, int* endPre, 
     int* startIn,  int* endIn){
int rootv = startPre[0];
BinaryTreeNode* root = new BinaryTreeNode();
root->m_value = rootv; 
root->m_left = root->m_right = NULL;
if (startPre == endPre){ //序列中只有一个值
if (startIn == endIn && *endPre == *endIn)
return root;
else
throw exception("Invalid input!");
}

int *rootIn = startIn;
while (rootIn != endIn && *rootIn != rootv)
++rootIn;
if (rootIn == endIn && *rootIn != rootv) //序列中有多个值
throw exception("Invalid input!");
int leftlen = rootIn - startIn;
int *leftend = startPre + leftlen;
if (leftlen > 0)
root->m_left = ConstructCore(startPre + 1, leftend, startIn, rootIn - 1);
if (leftlen < endPre - startPre)
root->m_right = ConstructCore(leftend + 1, endPre, rootIn + 1, endIn);
return root;
}
BinaryTreeNode* Construct(int* preorder, int* inorder, int len){
if (preorder == NULL || inorder == NULL || len <= 0)
return NULL;
return ConstructCore(preorder, preorder + len - 1, inorder, inorder + len - 1);
}
// ====================测试代码====================
void main06(){
//const int length = 8;
//int pre[length] = { 1, 2, 4, 7, 3, 5, 6, 8 };
//int in[length] = { 4, 7, 2, 1, 5, 3, 8, 6 };
//const int length = 5;
//int preorder[length] = { 1, 2, 3, 4, 5 };
//int inorder[length] = { 5, 4, 3, 2, 1 };
//const int length = 5;
//int preorder[length] = { 1, 2, 3, 4, 5 };
//int inorder[length] = { 1, 2, 3, 4, 5 };
//const int length = 1;
//int preorder[length] = { 1 };
//int inorder[length] = { 1 };
const int length = 7;
int preorder[length] = { 1, 2, 4, 5, 3, 6, 7 };
int inorder[length] = { 4, 2, 8, 1, 6, 3, 7 };
BinaryTreeNode* root = Construct(preorder, inorder, length);
if (root != nullptr){
printf("root value: %d\n", root->m_value);
if (root->m_left != NULL)
printf("root->left value: %d\n", root->m_left->m_value);
if (root->m_right != NULL)
printf("root->right value: %d", root->m_right->m_value);
}
}