515. 在每个树行中找最大值

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class Solution {
    public List<Integer> largestValues(TreeNode root) {

        LinkedList<Integer> list = new LinkedList<>();
        Queue<TreeNode> queue = new LinkedList<>();

        if (root == null){
            return list;
        }

        queue.add(root);

        while (!queue.isEmpty()){

            int size = queue.size();
            int max = queue.peek().val;

            for (int i = 0; i < size; i++) {

                TreeNode temp = queue.poll();

                if (temp.val > max){
                    max = temp.val;
                }

                if (temp.left != null){
                    queue.add(temp.left);
                }

                if (temp.right != null){
                    queue.add(temp.right);
                }
            }

            list.add(max);
        }

        return list;
    }
}

/**
 * 时间复杂度 O(n)
 * 空间复杂度 O(n)
 */

https://leetcode-cn.com/problems/find-largest-value-in-each-tree-row/