validate bst

validatebst.kt

    @Test
    fun test() {
        val n = BinaryNode(4)
                .apply {
                    addLeft(2).apply {
                        addLeft(1)
                    }
                    addRight(6).apply {
                        addRight(7)
                    }
                }

        assert(validateBst1(n))
        assert(validateBst2(n, Int.MIN_VALUE, Int.MAX_VALUE))
        n.addLeft(10)
        assert(validateBst2(n, Int.MIN_VALUE, Int.MAX_VALUE) == false)
    }

    fun validateBst1(node: BinaryNode<Int>?): Boolean {
        if (node == null) return true
        if (node.left == null && node.right == null) return true;

        var left : Boolean = false
        var right: Boolean = false

        if (node.left == null || node.data >= node.left!!.data) {
            left =  validateBst1(node.left)
        }

        if (node.right == null || node.data <= node.right!!.data) {
            right = validateBst1(node.right)
        }

        return left && right
    }

    fun validateBst2(node: BinaryNode<Int>?, min: Int, max: Int): Boolean {
        if (node == null) return true
        if (node.data !in min..max) return false
        return validateBst2(node.left, min, node.data) && validateBst2(node.right, node.data, max)
    }