Why does the fastest solution work when there is no && between last two return statements?


In the fastest solution for this problem there is no and between the return of isBalanced(A->left) and return of isBalanced(A->right) thus if left tree is balanced and the right tree is not then also it returns true .
But still the solution works for all test aes! why is so? there must be && operator between the last two return statements.


the return method is int not boolean therefore it should be only one & not &&