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  • 1315. Sum of Nodes with Even-Valued Grandparent

    package LeetCode_1315
    
    import java.util.*
    
    /**
     * 1315. Sum of Nodes with Even-Valued Grandparent
     * https://leetcode.com/problems/sum-of-nodes-with-even-valued-grandparent/
     * Given a binary tree, return the sum of values of nodes with even-valued grandparent.
     * (A grandparent of a node is the parent of its parent, if it exists.)
    If there are no nodes with an even-valued grandparent, return 0.
    
    Constraints:
    1. The number of nodes in the tree is between 1 and 10^4.
    2. The value of nodes is between 1 and 100.
     * */
    class TreeNode(var `val`: Int) {
        var left: TreeNode? = null
        var right: TreeNode? = null
    }
    
    class Solution {
        /*
        * solution: BFS, traversal tree level by level, Time: O(n), Space:O(n)
        * */
        fun sumEvenGrandparent(root: TreeNode?): Int {
            if (root == null) {
                return 0
            }
            var result = 0
            val queue = LinkedList<TreeNode>()
            queue.offer(root)
            while (queue.isNotEmpty()) {
                val cur = queue.pop()
                //checking cur's left child
                if (cur.left != null) {
                    queue.offer(cur.left)
                    if (cur.`val` % 2 == 0) {
                        //checking cur's left Grandson and right Grandson
                        if (cur.left!!.left != null) {
                            result += cur.left!!.left!!.`val`
                        }
                        if (cur.left!!.right != null) {
                            result += cur.left!!.right!!.`val`
                        }
                    }
                }
                //checking cur's right child
                if (cur.right != null) {
                    queue.offer(cur.right)
                    if (cur.`val` % 2 == 0) {
                        //checking cur's left Grandson and right Grandson
                        if (cur.right!!.left != null) {
                            result += cur.right!!.left!!.`val`
                        }
                        if (cur.right!!.right != null) {
                            result += cur.right!!.right!!.`val`
                        }
                    }
                }
            }
            return result
        }
    }
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  • 原文地址:https://www.cnblogs.com/johnnyzhao/p/13954445.html
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