110. Balanced Binary Tree
Code
```cpp
class Solution {
public:
bool isBalanced(TreeNode* root) {
bool ans = true;
auto balance = [&](const auto& self, const auto& root) -> int {
if (root == nullptr) return 0;
int left = self(self, root -> left);
int right = self(self, root -> right);
ans = ans & (abs(left - right) <= 1);
return max(left, right) + 1;
};
balance(balance, root);
return ans;
}
};
```