Leetcode 105 Construct Binary Tree from Preorder and Inorder Traversal

/**
* 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* ConstructTree(vector<int> &preorder, int preStart, int preEnd, vector<int> &inorder, int inStart, int inEnd)
{
if(preStart > preEnd)
{
return NULL;
}

TreeNode* root = new TreeNode(0);
root->val = preorder[preStart];

if(preEnd == preStart)
{
return root;
}

int i;
for(i=0; i < inorder.size(); ++i)
{
if(root->val == inorder[i+inStart])
{
break;
}
}

root->left = ConstructTree(preorder, preStart+1, preStart+i, inorder, inStart, inStart+i-1);
root->right = ConstructTree(preorder, i+preStart+1, preEnd, inorder, inStart+i+1,inEnd);

return root;
}

TreeNode* buildTree(vector<int>& preorder, vector<int>& inorder) {
if(preorder.size() <= 0)
{
return NULL;
}

if(preorder.size() != inorder.size())
{
return NULL;
}

TreeNode* node = new TreeNode(0);
node = ConstructTree(preorder, 0, preorder.size()-1, inorder, 0, inorder.size()-1);
return node;
}
};

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