LeetCode之Univalued Binary Tree（Kotlin）

問題： A binary tree is univalued if every node in the tree has the same value. Return true if and only if the given tree is univalued.

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方法： 先儲存根節點的val，然後遞迴遍歷整個tree，如果有某個節點的val不等於根節點的val則返回false，否則返回true，遍歷的結果即為最終結果。

具體實現：

class UnivaluedBinaryTree {
    // Definition for a binary tree node.
    class TreeNode(var `val`: Int = 0) {
        var left: TreeNode? = null
        var right: TreeNode? = null
    }

    private var uniValue = 0

    fun isUnivalTree(root: TreeNode?): Boolean {
        if(root == null) {
            return false
        } else {
            uniValue = root.`val`
            return isUnivalTreeInternal(root.left) && isUnivalTreeInternal(root.right)
        }
    }

    fun isUnivalTreeInternal(root: TreeNode?): Boolean {
        if(root == null) {
            return true
        } else {
            return isUnivalTreeInternal(root.left) && isUnivalTreeInternal(root.right) && root.`val` == uniValue
        }
    }
}

fun main(args: Array<String>) {

}
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具體程式碼實現可以參考Github