constructMaximumBinaryTree

/**
 * 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* buildTree(vector<int>& nums, int l, int r) {
        // Base case: no elements
        if (l > r) return nullptr;

        // Find index of maximum element
        int maxIndex = l;
        for (int i = l + 1; i <= r; i++) {
            if (nums[i] > nums[maxIndex]) {
                maxIndex = i;
            }
        }

        // Create root node
        TreeNode* root = new TreeNode(nums[maxIndex]);

        // Recursively build left and right subtrees
        root->left = buildTree(nums, l, maxIndex - 1);
        root->right = buildTree(nums, maxIndex + 1, r);

        return root;
    }

    TreeNode* constructMaximumBinaryTree(vector<int>& nums) {
        return buildTree(nums, 0, nums.size() - 1);
    }
};