LeetCode: Find Largest Value in Each Tree Row

LeetCode: Find Largest Value in Each Tree Row

You need to find the largest value in each row of a binary tree.

Example:

1
2
3
4
5
6
7
8
9
Input:

1
/ \
3 2
/ \ \
5 3 9

Output: [1, 3, 9]
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
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25
26
27
28
29
30
31
32
33
34
/**
* Definition for a binary tree node.
* public class TreeNode {
* int val;
* TreeNode left;
* TreeNode right;
* TreeNode(int x) { val = x; }
* }
*/
public class Solution {
public List<Integer> largestValues(TreeNode root) {
List<Integer> result = new ArrayList<>();
if (root == null) {
return result;
}
Queue<TreeNode> queue = new LinkedList<>();
queue.add(root);
queue.add(null);
int max = Integer.MIN_VALUE;
while (!queue.isEmpty()) {
TreeNode node = queue.poll();
if (node == null) {
result.add(max);
max = Integer.MIN_VALUE;
if (!queue.isEmpty())queue.add(null);
} else {
max = Math.max(max, node.val);
if (node.left != null) queue.add(node.left);
if (node.right != null) queue.add(node.right);
}
}
return result;
}
}