[LeetCode]Construct Binary Tree from Inorder and Postorder Traversal

题目描述:(链接)

Given inorder and postorder 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>& inorder, vector<int>& postorder) {
        return buildTree(begin(inorder), end(inorder), begin(postorder), end(postorder));
    }
private:
    TreeNode *buildTree(vector<int>::iterator in_first, vector<int>::iterator in_last, 
                        vector<int>::iterator post_first, vector<int>::iterator post_last) {
        if (in_first == in_last) return nullptr;
        if (post_first == post_last) return nullptr;
        
        auto val = *prev(post_last);
        TreeNode *root = new TreeNode(val);
        auto in_root_pos = find(in_first, in_last, val);
        auto in_left_size = distance(in_first, in_root_pos);
        auto post_left_last = next(post_first, in_left_size);
        
        root->left = buildTree(in_first, in_root_pos, post_first, post_left_last);
        root->right = buildTree(next(in_root_pos), in_last, post_left_last, prev(post_last));
        
    }
};