1161. 最大层内元素和

中等

题目描述

解题思路:
使用广度优先搜索 bfs ，记录每行的最大值与行号

class Solution {
    int level = 0;
    int res = -1;
    int max = -65535;
    public int maxLevelSum(TreeNode root) {
        List<TreeNode> list = new ArrayList<>();
        list.add(root);
        while ((list = bfs(list)).size() != 0);
        return res;
    }

    public List<TreeNode> bfs(List<TreeNode> nodes){
        level++;
        int sum = 0;
        List<TreeNode> list = new ArrayList<TreeNode>();
        for (int i = 0; i < nodes.size(); i++) {
            TreeNode node = nodes.get(i);
            sum += node.val;
            if(node.left != null) list.add(node.left);
            if(node.right != null) list.add(node.right);
        }
        if(sum > max)  {res = level;max = sum;}
        return list;
    }
}