[LeetCode April Challange] Day 11 - Deepest Leaves Sum

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

---

Solution

Level Order Traversal

Time complexity : O(n)
Space complexity : O(n)

/**
* 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 {
public:
    int deepestLeavesSum(TreeNode* root) {
        int ans = 0, i = 0;
        queue<TreeNode*> q;
        q.push(root);
        while (!q.empty()) {
            for (i=q.size()-1, ans=0; 0<=i; --i) {
                TreeNode *cur = q.front(); q.pop();
                ans += cur->val;
                if (cur->left) q.push(cur->left);
                if (cur->right) q.push(cur->right);
            }
        }
        return ans;
    }
};