[LeetCode] Construct Binary Tree from Preorder and Inorder Traversal

Given preorder and inorder traversal of a tree, construct the binary tree.

Note:
You may assume that duplicates do not exist in the tree.

 

/**
 * Definition for binary tree
 * struct TreeNode {
 *     int val;
 *     TreeNode *left;
 *     TreeNode *right;
 *     TreeNode(int x) : val(x), left(NULL), right(NULL) {}
 * };
 */
class Solution {
public:
    template<typename Iter>
    TreeNode *buildTree(Iter preBegin, Iter preEnd, Iter inBegin, Iter inEnd) {
        if (preBegin > preEnd) return nullptr;
        if (inBegin > inEnd) return nullptr;
        
        int root_val = *preBegin;
        TreeNode *root = new TreeNode(root_val);
        Iter in_root_pos = find(inBegin, inEnd, root_val);
        int left_size = in_root_pos - inBegin;
        root->left = buildTree(preBegin + 1, preBegin + left_size, inBegin, in_root_pos - 1);
        root->right = buildTree(preBegin + left_size + 1, preEnd, in_root_pos + 1, inEnd);
        
        return root;
    }
    
    TreeNode *buildTree(vector<int> &preorder, vector<int> &inorder) {
        if (preorder.empty() || inorder.empty())
            return NULL;
            
        return buildTree(preorder.begin(), preorder.end() - 1, inorder.begin(), inorder.end() - 1);
    }
};