Kotlin Leetcode - 965. Univalued Binary Tree

題目連接

/**
 * 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 isUnivalTree(root: TreeNode?): Boolean {
        
    }
}

解題思路

這一題考的是對樹的處理

和 100. Same Tree 一樣

可以單純的透過遞迴判斷

Kotlin 參考解答

點擊展開解答

class Solution {
    fun isUnivalTree(root: TreeNode?): Boolean {
        return (root == null)
                || (root.left == null || root.`val` == root.left.`val`)
                && (root.right == null || root.`val` == root.right.`val`)
                && isUnivalTree(root.left) && isUnivalTree(root.right)
    }
}

上述邏輯也可以透過 when 來改寫

class Solution {
    fun isUnivalTree(root: TreeNode?): Boolean {
        return when {
            root == null -> true
            root.left != null && root.`val` != root.left.`val` -> false
            root.right != null && root.`val` != root.right.`val` -> false
            else -> isUnivalTree(root.left) && isUnivalTree(root.right)
        }
    }
}

---

回到 leetcode 列表