【Leetcode C++】1382. Balance a Binary Search Tree

1382. Balance a Binary Search Tree

/**
 * 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:
    vector<int> V;
    void inOrder(TreeNode* root) {
    
    
        if(!root) return ;
        inOrder(root->left);
        V.push_back(root->val);
        inOrder(root->right);
    }
    TreeNode* balanceBST(int l, int r) {
    
    
        if(l >= r) return NULL;
        int mid = (l + r) / 2;
        TreeNode* root = new TreeNode(V[mid]);
        root->left = balanceBST(l, mid);
        root->right = balanceBST(mid + 1, r);
        return root;
    }
    TreeNode* balanceBST(TreeNode* root) {
    
    
        inOrder(root);
        return balanceBST(0, V.size());
    }
};