515. Find Largest Value In Each Tree Row¶

515. Find Largest Value in Each Tree Row

Medium

Given the root of a binary tree, return an array of the largest value in each row of the tree (0-indexed).

Example 1:

Input: root = [1,3,2,5,3,null,9]
Output: [1,3,9]

Example 2:

Input: root = [1,2,3]
Output: [1,3]

Constraints:

The number of nodes in the tree will be in the range [0, 10⁴].
-2³¹ <= Node.val <= 2³¹ - 1

Solution¶

/**
 * 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> ans = new ArrayList<>();
        Queue<TreeNode> q = new LinkedList<>();
        if(root == null) return ans;
        q.offer(root);
        while(!q.isEmpty()){
            int len = q.size();
            int max = q.peek().val;
            for(int i = 0; i < len; i++){
                if(q.peek().left != null) q.offer(q.peek().left);
                if(q.peek().right != null) q.offer(q.peek().right);
                max = Math.max(max, q.poll().val);
            }
            ans.add(max);
        }
        return ans;
    }
}

Complexity Analysis¶

Time Complexity: O(?)
Space Complexity: O(?)

Explanation¶

[Add detailed explanation here]