515. Find Largest Value in Each Tree Row

Runtime    2 ms
Beats      82.84%


Memory     44.2 MB
Beats      35.69%


/**
 * 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> result = new ArrayList<>();
        if(root != null) {
            Queue<TreeNode> queue = new LinkedList<>();
            queue.add(root);
            while(!queue.isEmpty()) {
                int size = queue.size(), max = Integer.MIN_VALUE;
                for(int i=0;i<size;i++) {
                    TreeNode node = queue.poll();
                    max = Math.max(max, node.val);
                    if(node.left != null) queue.add(node.left);
                    if(node.right != null) queue.add(node.right);
                }
                result.add(max);
            }
        }
        return result; 
    }
}