LeetCode in Kotlin

2331. Evaluate Boolean Binary Tree

Easy

You are given the root of a full binary tree with the following properties:

• Leaf nodes have either the value 0 or 1, where 0 represents False and 1 represents True.
• Non-leaf nodes have either the value 2 or 3, where 2 represents the boolean OR and 3 represents the boolean AND.

The evaluation of a node is as follows:

• If the node is a leaf node, the evaluation is the value of the node, i.e. True or False.
• Otherwise, evaluate the node’s two children and apply the boolean operation of its value with the children’s evaluations.

Return the boolean result of evaluating the root node.

A full binary tree is a binary tree where each node has either 0 or 2 children.

A leaf node is a node that has zero children.

Example 1:

Input: root = [2,1,3,null,null,0,1]

Output: true

Explanation: The above diagram illustrates the evaluation process.

The AND node evaluates to False AND True = False.

The OR node evaluates to True OR False = True.

The root node evaluates to True, so we return true.

Example 2:

Input: root = [0]

Output: false

Explanation: The root node is a leaf node and it evaluates to false, so we return false.

Constraints:

• The number of nodes in the tree is in the range [1, 1000].
• 0 <= Node.val <= 3
• Every node has either 0 or 2 children.
• Leaf nodes have a value of 0 or 1.
• Non-leaf nodes have a value of 2 or 3.

Solution

import com_github_leetcode.TreeNode

class Solution {
    fun evaluateTree(root: TreeNode?): Boolean {
        return if (root!!.left == null) {
            root.`val` == 1
        } else {
            if (root.`val` == 2) {
                evaluateTree(root.left) || evaluateTree(root.right)
            } else {
                evaluateTree(root.left) && evaluateTree(root.right)
            }
        }
    }
}

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