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Formatted question description: https://leetcode.ca/all/1302.html

# 1302. Deepest Leaves Sum (Medium)

Given 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


Constraints:

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

Related Topics:
Tree, Depth-first Search

## Solution 1. DFS

// OJ: https://leetcode.com/problems/deepest-leaves-sum/
// Time: O(N)
// Space: O(H)
class Solution {
int getDepth(TreeNode *root) {
return root ? 1 + max(getDepth(root->left), getDepth(root->right)) : 0;
}
int getSumAtDepth(TreeNode *root, int d, int depth) {
if (!root) return 0;
if (d == depth) return root->val;
return getSumAtDepth(root->left, d + 1, depth) + getSumAtDepth(root->right, d + 1, depth);
}
public:
int deepestLeavesSum(TreeNode* root) {
int depth = getDepth(root);
return getSumAtDepth(root, 1, depth);
}
};


## Solution 2. BFS

// OJ: https://leetcode.com/problems/deepest-leaves-sum/
// Time: O(N)
// Space: O(N)
class Solution {
public:
int deepestLeavesSum(TreeNode* root) {
if (!root) return 0;
queue<TreeNode*> q;
q.push(root);
int ans;
q.push(root);
while (q.size()) {
int cnt = q.size();
ans = 0;
while (cnt--) {
auto node = q.front();
q.pop();
ans += node->val;
if (node->left) q.push(node->left);
if (node->right) q.push(node->right);
}
}
return ans;
}
};

• /**
* Definition for a binary tree node.
* public class TreeNode {
*     int val;
*     TreeNode left;
*     TreeNode right;
*     TreeNode(int x) { val = x; }
* }
*/
class Solution {
public int deepestLeavesSum(TreeNode root) {
if (root == null)
return 0;
queue.offer(root);
int deepestSum = 0;
while (!queue.isEmpty()) {
int curSum = 0;
int size = queue.size();
for (int i = 0; i < size; i++) {
TreeNode node = queue.poll();
curSum += node.val;
TreeNode left = node.left, right = node.right;
if (left != null)
queue.offer(left);
if (right != null)
queue.offer(right);
}
deepestSum = curSum;
}
return deepestSum;
}
}

############

/**
* Definition for a binary tree node.
* public class TreeNode {
*     int val;
*     TreeNode left;
*     TreeNode right;
*     TreeNode() {}
*     TreeNode(int val) { this.val = val; }
*     TreeNode(int val, TreeNode left, TreeNode right) {
*         this.val = val;
*         this.left = left;
*         this.right = right;
*     }
* }
*/
class Solution {
public int deepestLeavesSum(TreeNode root) {
Deque<TreeNode> q = new ArrayDeque<>();
q.offer(root);
int ans = 0;
while (!q.isEmpty()) {
ans = 0;
for (int n = q.size(); n > 0; --n) {
root = q.pollFirst();
ans += root.val;
if (root.left != null) {
q.offer(root.left);
}
if (root.right != null) {
q.offer(root.right);
}
}
}
return ans;
}
}

• // OJ: https://leetcode.com/problems/deepest-leaves-sum/
// Time: O(N)
// Space: O(H)
class Solution {
int getDepth(TreeNode *root) {
return root ? 1 + max(getDepth(root->left), getDepth(root->right)) : 0;
}
int getSumAtDepth(TreeNode *root, int d, int depth) {
if (!root) return 0;
if (d == depth) return root->val;
return getSumAtDepth(root->left, d + 1, depth) + getSumAtDepth(root->right, d + 1, depth);
}
public:
int deepestLeavesSum(TreeNode* root) {
int depth = getDepth(root);
return getSumAtDepth(root, 1, depth);
}
};

• # Definition for a binary tree node.
# class TreeNode:
#     def __init__(self, val=0, left=None, right=None):
#         self.val = val
#         self.left = left
#         self.right = right
class Solution:
def deepestLeavesSum(self, root: Optional[TreeNode]) -> int:
q = deque([root])
while q:
ans = 0
for _ in range(len(q)):
root = q.popleft()
ans += root.val
if root.left:
q.append(root.left)
if root.right:
q.append(root.right)
return ans

############

# 1302. Deepest Leaves Sum
# https://leetcode.com/problems/deepest-leaves-sum/

# Definition for a binary tree node.
# class TreeNode:
#     def __init__(self, val=0, left=None, right=None):
#         self.val = val
#         self.left = left
#         self.right = right
class Solution:
def deepestLeavesSum(self, root: TreeNode) -> int:
deq = collections.deque([root])
res = 0

while deq:
l = len(deq)
res = 0

while l:
node = deq.popleft()
res += node.val

for n in (node.left, node.right):
if n: deq.append(n)
l -= 1

return res

• /**
* Definition for a binary tree node.
* type TreeNode struct {
*     Val int
*     Left *TreeNode
*     Right *TreeNode
* }
*/
func deepestLeavesSum(root *TreeNode) int {
q := []*TreeNode{root}
ans := 0
for len(q) > 0 {
ans = 0
for n := len(q); n > 0; n-- {
root = q[0]
q = q[1:]
ans += root.Val
if root.Left != nil {
q = append(q, root.Left)
}
if root.Right != nil {
q = append(q, root.Right)
}
}
}
return ans
}

• /**
* Definition for a binary tree node.
* class TreeNode {
*     val: number
*     left: TreeNode | null
*     right: TreeNode | null
*     constructor(val?: number, left?: TreeNode | null, right?: TreeNode | null) {
*         this.val = (val===undefined ? 0 : val)
*         this.left = (left===undefined ? null : left)
*         this.right = (right===undefined ? null : right)
*     }
* }
*/

function deepestLeavesSum(root: TreeNode | null): number {
const queue = [root];
let res = 0;
while (queue.length !== 0) {
const n = queue.length;
let sum = 0;
for (let i = 0; i < n; i++) {
const { val, left, right } = queue.shift();
sum += val;
left && queue.push(left);
right && queue.push(right);
}
res = sum;
}
return res;
}


• // Definition for a binary tree node.
// #[derive(Debug, PartialEq, Eq)]
// pub struct TreeNode {
//   pub val: i32,
//   pub left: Option<Rc<RefCell<TreeNode>>>,
//   pub right: Option<Rc<RefCell<TreeNode>>>,
// }
//
// impl TreeNode {
//   #[inline]
//   pub fn new(val: i32) -> Self {
//     TreeNode {
//       val,
//       left: None,
//       right: None
//     }
//   }
// }
use std::rc::Rc;
use std::cell::RefCell;
impl Solution {
fn dfs(root: &Option<Rc<RefCell<TreeNode>>>, depth: i32, max_depth: &mut i32, res: &mut i32) {
if let Some(node) = root {
let node = node.borrow();
if node.left.is_none() && node.right.is_none() {
if depth == *max_depth {
*res += node.val;
} else if depth > *max_depth {
*max_depth = depth;
*res = node.val
}
return;
}
Self::dfs(&node.left, depth + 1, max_depth, res);
Self::dfs(&node.right, depth + 1, max_depth, res);
}
}

pub fn deepest_leaves_sum(root: Option<Rc<RefCell<TreeNode>>>) -> i32 {
let mut res = 0;
let mut max_depth = 0;
Self::dfs(&root, 0, &mut max_depth, &mut res);
res
}
}