随机图片网站,商城天气,网站建设有限公司,衡阳网站建设怎样收费提示#xff1a;文章写完后#xff0c;目录可以自动生成#xff0c;如何生成可参考右边的帮助文档 文章目录 前言一、力扣1161. 最大层内元素和二、力扣1302. 层数最深叶子节点的和三、力扣1609. 奇偶树 前言 有些二叉树的特殊技巧需要用层序遍历的方式来做#xff0c;比如… 提示文章写完后目录可以自动生成如何生成可参考右边的帮助文档 文章目录 前言一、力扣1161. 最大层内元素和二、力扣1302. 层数最深叶子节点的和三、力扣1609. 奇偶树 前言 有些二叉树的特殊技巧需要用层序遍历的方式来做比如下面列举的几道题。这类问题你当特殊题型记住就行了不会有太多变体的。
一、力扣1161. 最大层内元素和
/*** Definition for a binary tree node.* public class TreeNode {* int val;* TreeNode left;* TreeNode right;* TreeNode() {}* TreeNode(int val) { this.val val; }* TreeNode(int val, TreeNode left, TreeNode right) {* this.val val;* this.left left;* this.right right;* }* }*/
class Solution {public int maxLevelSum(TreeNode root) {int len Integer.MAX_VALUE;int sum Integer.MIN_VALUE;int depth 1;DequeTreeNode deq new ArrayDeque();deq.offerLast(root);while(!deq.isEmpty()){int count 0;int size deq.size();for(int i 0; i size; i ){TreeNode cur deq.pollFirst();count cur.val;if(cur.left ! null){deq.offerLast(cur.left);}if(cur.right ! null){deq.offerLast(cur.right);}}if(count sum){sum count;len depth;}depth ;}return len;}
}二、力扣1302. 层数最深叶子节点的和
/*** Definition for a binary tree node.* public class TreeNode {* int val;* TreeNode left;* TreeNode right;* TreeNode() {}* TreeNode(int val) { this.val val; }* TreeNode(int val, TreeNode left, TreeNode right) {* this.val val;* this.left left;* this.right right;* }* }*/
class Solution {public int deepestLeavesSum(TreeNode root) {int sum 0;DequeTreeNode deq new ArrayDeque();deq.offerLast(root);while(!deq.isEmpty()){int size deq.size();int count 0;for(int i 0; i size; i ){TreeNode cur deq.pollFirst();if(cur.left ! null){deq.offerLast(cur.left);}if(cur.right ! null){deq.offerLast(cur.right);}if(cur.left null cur.right null){count cur.val;}}sum count;}return sum;}
}三、力扣1609. 奇偶树
/*** Definition for a binary tree node.* public class TreeNode {* int val;* TreeNode left;* TreeNode right;* TreeNode() {}* TreeNode(int val) { this.val val; }* TreeNode(int val, TreeNode left, TreeNode right) {* this.val val;* this.left left;* this.right right;* }* }*/
class Solution {public boolean isEvenOddTree(TreeNode root) {if(root.val % 2 0){return false;}DequeTreeNode deq new ArrayDeque();deq.offerLast(root);int depth 0;while(!deq.isEmpty()){TreeNode pre null;int size deq.size();for(int i 0; i size; i ){TreeNode cur deq.pollFirst();if(cur.left ! null){deq.offerLast(cur.left);}if(cur.right ! null){deq.offerLast(cur.right);}if(depth % 2 0 cur.val % 2 0){return false;}if(depth % 2 1 cur.val % 2 1){return false;}if(pre ! null){if(depth % 2 0){if(pre.val cur.val){return false;}}else{if(pre.val cur.val){return false;}}}pre cur;}depth ;}return true;}
}
