#LeetCode：993. Cousins in Binary Tree

此題要問的是兩個數值在指定的二元樹中，是否深度相同但親節點不同。

基本上的方法就是先找出兩個數值在二元樹中的深度與其親節點為何，接著進行比較即可得解。

Kotlin(148ms)

/*******************************************************
 * LeetCode 993. Cousins in Binary Tree                *
 * Author: Maplewing [at] knightzone.studio            *
 * Version: 2020/05/07                                 *
 *******************************************************/
/**
 * 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 {
    companion object {
        const val ROOT_PARENT = -1
    }

    data class NodeData(val depth: Int, val parent: Int)

    fun findNode(root: TreeNode?, n: Int, depth: Int, parent: Int): NodeData? {
        if (root == null) return null

        if (root.`val` == n) {
          return NodeData(depth, parent)
        }  

        val leftFound = findNode(root.left, n, depth + 1, root.`val`)
        if (leftFound != null) return leftFound

        return findNode(root.right, n, depth + 1, root.`val`)
    }

    fun isCousins(root: TreeNode?, x: Int, y: Int): Boolean {
        if (root == null) return false

        var xNodeData = findNode(root, x, 0, ROOT_PARENT)
        var yNodeData = findNode(root, y, 0, ROOT_PARENT)

        return (xNodeData?.depth == yNodeData?.depth && 
            xNodeData?.parent != yNodeData?.parent) ?: false
    }
}