You need to find the largest value in each row of a binary tree.
Thoughts
每层最大值自然按层遍历即可。
Code
/**
* Definition for a binary tree node.
* public class TreeNode {
* int val;
* TreeNode left;
* TreeNode right;
* TreeNode(int x) { val = x; }
* }
*/
class Solution {
public List<Integer> largestValues(TreeNode root) {
List<Integer> res = new ArrayList<>();
if (root == null) {
return res;
}
Queue<TreeNode> queue = new LinkedList<>();
queue.add(root);
while (!queue.isEmpty()) {
int length = queue.size();
int max = Integer.MIN_VALUE;
for (int i = 0; i < length; i++) {
TreeNode node = queue.remove();
max = Math.max(max, node.val);
if (node.left != null) queue.add(node.left);
if (node.right != null) queue.add(node.right);
}
res.add(max);
}
return res;
}
}