Find Largest Value in Each Tree Row

You need to find the largest value in each row of a binary tree.Have you met this question in a real interview? YesProblem Correction

Example

Input: [1,3,2,5,3,#,9]
Output: [1, 3, 9]

和层序遍历的题基本一样，只是加上个找最大值

/**
 * Definition of TreeNode:
 * public class TreeNode {
 *     public int val;
 *     public TreeNode left, right;
 *     public TreeNode(int val) {
 *         this.val = val;
 *         this.left = this.right = null;
 *     }
 * }
 */

public class Solution {
    /**
     * @param root: a root of integer
     * @return: return a list of integer
     */
    public List<Integer> largestValues(TreeNode root) {
        // write your code here
        
        List<Integer> list = new ArrayList<>();
        
        if(root == null)
            return list;
            
        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();
                if(node.left != null){
                    queue.offer(node.left);
                }
                
                if(node.right != null){
                    queue.offer(node.right);
                }
                max = Math.max(max,node.val);
            } 
            
            list.add(max);
            
        }
        
        
        return list;
        
    }
}