题目链接

层序遍历

/*** 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 List<Integer> largestValues(TreeNode root) {List<Integer> list = new ArrayList();Deque<TreeNode> queue = new LinkedList<TreeNode>();if(root != null){queue.offer(root);}while(!queue.isEmpty()){int size = queue.size();// Java最小值整型常量表示方法int max = Integer.MIN_VALUE;for(int i = 0; i < size; i++){TreeNode node = queue.poll();if(node.val > max){max = node.val;}if(node.left != null){queue.offer(node.left);}if(node.right != null){queue.offer(node.right);}}list.add(max);}return list;}
}