g0201_0300.s0222_count_complete_tree_nodes.Solution.kt Maven / Gradle / Ivy

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Kotlin-based LeetCode algorithm problem solutions, regularly updated

There is a newer version: 1.30

package g0201_0300.s0222_count_complete_tree_nodes

import com_github_leetcode.TreeNode

/*
 * Example:
 * var ti = TreeNode(5)
 * var v = ti.`val`
 * Definition for a binary tree node.
 * class TreeNode(var `val`: Int) {
 *     var left: TreeNode? = null
 *     var right: TreeNode? = null
 * }
 */
class Solution {
    fun countNodes(root: TreeNode?): Int {
        if (root == null) {
            return 0
        }
        val leftHeight = leftHeight(root)
        val rightHeight = rightHeight(root)
        // case 1: When Height(Left sub-tree) = Height(right sub-tree) 2^h - 1
        return if (leftHeight == rightHeight) {
            (1 shl leftHeight) - 1
        } else {
            1 + countNodes(root.left) + countNodes(root.right)
        }
    }

    private fun leftHeight(root: TreeNode?): Int {
        return if (root == null) {
            0
        } else 1 + leftHeight(root.left)
    }

    private fun rightHeight(root: TreeNode?): Int {
        return if (root == null) {
            0
        } else 1 + rightHeight(root.right)
    }
}