1302. Deepest Leaves Sum

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

/**
 * Definition for a binary tree node.
 * struct TreeNode {
 *     int val;
 *     TreeNode *left;
 *     TreeNode *right;
 *     TreeNode() : val(0), left(nullptr), right(nullptr) {}
 *     TreeNode(int x) : val(x), left(nullptr), right(nullptr) {}
 *     TreeNode(int x, TreeNode *left, TreeNode *right) : val(x), left(left), right(right) {}
 * };
 */
class Solution {
    map<int, int> sum;
public:
    int deepestLeavesSum(TreeNode* root, int level = 0) {
        if(!root) return -1;
        sum[level] += root->val;
        deepestLeavesSum(root->left, level + 1);
        deepestLeavesSum(root->right, level + 1);
        return sum.rbegin()->second;
    }
};