#leetcode#515. Find Largest Element in Each Row

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515. Find Largest Element in Each Row

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User Accepted: 851
User Tried: 878
Total Accepted: 943
Total Submissions: 2140
Difficulty: Medium

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

Example:

Input:           1         / \        3   2       / \   \        5   3   9 Output: [1, 3, 9]

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还是一道BFS的题，每层记录一下当前层的最大值即可，值得注意的是这里当input为null时要求返回的是一个空的array，当然实际面试时返回null也不无不可

/** * Definition for a binary tree node. * public class TreeNode { *     int val; *     TreeNode left; *     TreeNode right; *     TreeNode(int x) { val = x; } * } */public class Solution {    public int[] findValueMostElement(TreeNode root) {        if(root == null)    return new int[0];        List<Integer> list = new ArrayList<>();        LinkedList<TreeNode> queue = new LinkedList<>();        queue.offer(root);        while(!queue.isEmpty()){            int tmpMax = Integer.MIN_VALUE;            int size = queue.size();            for(int i = 0; i < size; i++){                TreeNode cur = queue.poll();                tmpMax = Math.max(tmpMax, cur.val);                if(cur.left != null)    queue.offer(cur.left);                if(cur.right != null)   queue.offer(cur.right);            }            list.add(tmpMax);        }        int[] res = new int[list.size()];        for(int j = 0; j < list.size(); j++){            res[j] = list.get(j);        }                return res;    }}

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