leetcode---Construct Binary Tree from Preorder and Inorder Traversal---树的构建

/**
* Definition for a binary tree node.
* struct TreeNode {
*     int val;
*     TreeNode *left;
*     TreeNode *right;
*     TreeNode(int x) : val(x), left(NULL), right(NULL) {}
* };
*/
class Solution
{
public:
TreeNode *makes(vector<int>& preorder, int preLow, int preHigh, vector<int>& inorder, int inLow, int inHigh)
{
if(preLow > preHigh)
return NULL;
else if(preLow == preHigh)
return new TreeNode(preorder[preLow]);
TreeNode *h = new TreeNode(preorder[preLow]);  //根节点
int i = inLow;   //根节点在中序遍历中的下标
for(; i<=inHigh; i++)
{
if(inorder[i] == preorder[preLow])
break;
}
int leftLen = i - inLow;
h->left = makes(preorder, preLow+1, preLow+leftLen, inorder, inLow, inLow+leftLen-1);
h->right = makes(preorder, preLow+leftLen+1, preHigh, inorder, inLow+leftLen+1, inHigh);
return h;
}

TreeNode* buildTree(vector<int>& preorder, vector<int>& inorder)
{
return makes(preorder, 0, preorder.size()-1, inorder, 0, inorder.size()-1);
}
};