1302. Deepest Leaves Sum (M)

题目

Given the root of a binary tree, return the sum of values of its deepest leaves.

Example 1:

Input: root = [1,2,3,4,5,null,6,7,null,null,null,null,8]
Output: 15

Example 2:

Input: root = [6,7,8,2,7,1,3,9,null,1,4,null,null,null,5]
Output: 19

Constraints:

• The number of nodes in the tree is in the range [1, 10^4].
• 1 <= Node.val <= 100

题意

计算二叉树最后一层结点的和。

思路

直接层序遍历。

代码实现

Java

class Solution {
    public int deepestLeavesSum(TreeNode root) {
        if (root == null) return 0;
        int sum = 0;
        Queue<TreeNode> q = new LinkedList<>();
        q.offer(root);
        while (!q.isEmpty()) {
            sum = 0;
            int size = q.size();
            while (size > 0) {
                TreeNode cur = q.poll();
                if (cur.left != null) q.offer(cur.left);
                if (cur.right != null) q.offer(cur.right);
                sum += cur.val;  
                size--;
            }
        }
        return sum;
    }
}