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[leetcode] problem 515 – find largest value in each tree row

admin 11月 13, 2020 0

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

Example

Input:

Output: [1, 3, 9]

Code

public class  {
    int val;
    TreeNode left;
    TreeNode right;
    TreeNode(int x) { val = x; }
}

public List<Integer> largestValues(TreeNode root) {
    List<Integer> result = new ArrayList<>();

    if (root == null)
        return result;

    Queue<TreeNode> queue = new LinkedList<>();
    queue.offer(root);

    while (!queue.isEmpty()) {
        int size = queue.size();
        int 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.offer(node.left);
            if (node.right != null)
                queue.offer(node.right);
        }

        result.add(max);
    }

    return result;
}