bool checkBalanced(TreeNode* root, int& len){

if(root == NULL) {

len = 0;

return true;

}

if(root -> left == NULL && root -> right == NULL){

len = 1;

return true;

}

int left = 0;

int right = 0;

bool l = checkBalanced(root -> left, left);

bool r = checkBalanced(root -> right, right);

len = max(left, right) + 1;

return l && r && abs(left - right) <= 1;

}

bool isBalanced(TreeNode *root) {

// Note: The Solution object is instantiated only once and is reused by each test case.

int len = 0;

return checkBalanced(root, len);

}