/**
 * 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 {
    TreeNode* construct(vector<int> nums,int start, int end)
    {
        if(start>end)
            return NULL;

        int i,index,v = INT_MIN;
        for(i=start;i<=end;i++)

            if(nums[i]>v)
            {
                v = nums[i];
                index = i;
            }
        }

        TreeNode* root = new TreeNode(v);
        root->left = construct(nums,start,index-1);
        root->right = construct(nums,index+1,end);
        return root;
    }
public:
    TreeNode* constructMaximumBinaryTree(vector<int>& nums) {
        return construct(nums,0,nums.size()-1);
    }
};

Line 27: 'root' does not name a type