1302. Deepest Leaves Sum

Link: https://leetcode.cn/problems/deepest-leaves-sum/

Question

difficulty: mid
adj diff: 3

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, 104].
    1 <= Node.val <= 100

Code

int sum;
int maxLevel;

public int deepestLeavesSum(TreeNode root) {
    dfs(root, 1);
    return sum;
}

private void dfs(TreeNode node, int level) {
    if (node == null) return;
    if (level > maxLevel) {
        maxLevel = level;
        sum = node.val;
    } else if (level == maxLevel) {
        sum += node.val;
    }
    dfs(node.left, level + 1);
    dfs(node.right, level + 1);
}