/**
 * Definition for a binary tree node.
 * struct TreeNode {
 *     int val;
 *     TreeNode *left;
 *     TreeNode *right;
 *     TreeNode() : val(0), left(nullptr), right(nullptr) {}
 *     TreeNode(int x) : val(x), left(nullptr), right(nullptr) {}
 *     TreeNode(int x, TreeNode *left, TreeNode *right) : val(x), left(left), right(right) {}
 * };
 */
class Solution {
public:
    TreeNode* get_big_tree(vector<int>& nums)
    {
        if(nums.size() == 0) return nullptr;
        TreeNode* root = new TreeNode;
        auto max_val =  max_element(nums.begin() , nums.end());
        root->val = *max_val;
        // cout<<*max_val<<' '<<max_val - nums.begin()<<endl;
        vector<int> left_nums(nums.begin() ,   max_val );
        vector<int> right_nums(  max_val  + 1 , nums.end());
        root->left = get_big_tree(left_nums);
        root->right = get_big_tree(right_nums);
        return root;
    }
    TreeNode* constructMaximumBinaryTree(vector<int>& nums) {
        if(nums.size() == 0) return nullptr;
        return get_big_tree(nums);
    }
};

/**
 * Definition for a binary tree node.
 * struct TreeNode {
 *     int val;
 *     TreeNode *left;
 *     TreeNode *right;
 *     TreeNode() : val(0), left(nullptr), right(nullptr) {}
 *     TreeNode(int x) : val(x), left(nullptr), right(nullptr) {}
 *     TreeNode(int x, TreeNode *left, TreeNode *right) : val(x), left(left), right(right) {}
 * };
 */
class Solution {
public:
    TreeNode* track_back(vector<int>& nums)
    {
        if(nums.size()==0) return nullptr;
        int max_num = 0;
        for(int i=0 ; i<nums.size();i++)
            if( nums[i] > nums[max_num] ) max_num = i;
        TreeNode* root = new TreeNode(nums[max_num]);
        if(nums.size() ==1 ) return root;
        vector<int> leftNums(nums.begin() , nums.begin() + max_num );
        vector<int> rightNums(nums.begin() + max_num +1 , nums.end());
        root->left =  track_back(leftNums);
        root->right = track_back(rightNums);
        return root;
    }
    TreeNode* constructMaximumBinaryTree(vector<int>& nums) {
        TreeNode* root = track_back(nums);
        return root;
    }
};