Force deduction solution summary 515- find the maximum value in each tree row

  Directory links ：

Force buckle programming problem - The solution sums up _ Share + Record -CSDN Blog

GitHub Synchronous question brushing items ：

https://github.com/September26/java-algorithms

Original link ： Power button

describe ：

Given the root node of a binary tree  root , Please find the maximum value of each layer in the binary tree .

Example 1：

Input : root = [1,3,2,5,3,null,9]
Output : [1,3,9]
Example 2：

Input : root = [1,2,3]
Output : [1,3]
 

Tips ：

The range of the number of nodes in a binary tree is [0,104]
-231 <= Node.val <= 231 - 1

source ： Power button （LeetCode）
link ：https://leetcode.cn/problems/find-largest-value-in-each-tree-row
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Their thinking ：

*  Their thinking ：
*  use list Record the maximum value of each level . Yes TreeNode Do recursive traversal , Incoming value is hierarchy / Nodes and list.

Code ：

public class Solution515 {

    public List<Integer> largestValues(TreeNode root) {
        List<Integer> list = new ArrayList<>();
        if (root == null) {
            return list;
        }
        search(0, root, list);
        return list;
    }

    private void search(int level, TreeNode node, List<Integer> list) {
        if (list.size() <= level) {
            list.add(node.val);
        } else {
            list.set(level, Math.max(list.get(level), node.val));
        }

        if (node.left != null) {
            search(level + 1, node.left, list);
        }
        if (node.right != null) {
            search(level + 1, node.right, list);
        }
    }
}