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# Deepest Leaves Sum

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

**Example 1:**

![](https://assets.leetcode.com/uploads/2019/07/31/1483_ex1.png)

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

**Constraints:**

* The number of nodes in the tree is between `1` and `10^4`.
* The value of nodes is between `1` and `100`.

```java
class Solution {
    public int deepestLeavesSum(TreeNode root) {
        Queue<TreeNode> q = new LinkedList<>();
        q.add(root);
        int ans = 0;
        while (q.size() != 0) {
            int sum = 0, size = q.size();
            while (size-- > 0) {
                TreeNode node = q.poll();
                if (node.left != null)
                    q.add(node.left);
                if (node.right != null)
                    q.add(node.right);
                sum += node.val;
            }
            if (q.size() == 0)
                ans = sum;
        }
        return ans;
    }
}
```