[LeetCode]Construct Binary Tree from Preorder and Inorder Traversal

题目描述:(链接)

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

解题思路：

/**
 * 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* buildTree(vector<int>& preorder, vector<int>& inorder) {
        return buildTree(begin(preorder), end(preorder), begin(inorder), end(inorder));
    }
    
private:
    TreeNode *buildTree(vector<int>::iterator p_first, vector<int>::iterator p_last, 
                        vector<int>::iterator i_first, vector<int>::iterator i_last) {
        if (p_first == p_last) return nullptr;
        if (i_first == i_last) return nullptr;
        
        auto root = new TreeNode(*p_first);
        auto inRootPos = find(i_first, i_last, *p_first);
        auto leftSize = distance(i_first, inRootPos);
        
        root->left = buildTree(next(p_first), next(p_first, leftSize + 1), i_first, next(i_first, leftSize));
        root->right = buildTree(next(p_first, leftSize + 1), p_last, next(inRootPos), i_last);
        
        return root;
    }
};