Leetcode Balanced Binary Tree problem solution

class Solution:
    def isBalanced(self, root: TreeNode) -> bool:
        d = {}
        def ifbalanced(node):
            if not node:
                d[node] = 0
                return True
            elif not ifbalanced(node.left) or not ifbalanced(node.right):
                return False
            else:
                d[node] = max(d[node.left],d[node.right])+1
                return True if abs(d[node.left]-d[node.right]) <2 else False

        
        return ifbalanced(root)

class Solution {
    int max = 0;
    public boolean isBalanced(TreeNode root) {
        depth(root);
        return max <= 1; 
    }
    public int depth(TreeNode root) {
        if(root==null) return 0;
        int left = depth(root.left);
        int right = depth(root.right);
        max = Math.max(Math.abs(left-right), max);
        return 1 + Math.max(left, right);
    }
}

class Solution {
public:
    int height(TreeNode* root){
        if(root==NULL)
            return 0;
        return max(height(root->left),height(root->right)) + 1;
    }
    bool isBalanced(TreeNode* root) {
        if(root==NULL)
            return true;
        return abs(height(root->left) - height(root->right))<=1 && isBalanced(root->right) && isBalanced(root->left);
    }
};

bool isBalanced(struct TreeNode* root) {
    bool ans = true;
    isBalancedHelper(root, &ans);
    return ans;
}

int isBalancedHelper(struct TreeNode * root, bool *answer) {
    if(!root) return 0;
    
    int left = isBalancedHelper(root -> left, answer);
    int right = isBalancedHelper(root -> right, answer);
    
    if(abs(left - right) > 1) {
        *answer = false;
    }
    
    return left > right ? left + 1 : right + 1;
}