# [LeetCode] 404. Sum of Left Leaves

## Problem

Find the sum of all left leaves in a given binary tree.

Example:

``````    3
/ \
9  20
/  \
15   7
``````

There are two left leaves in the binary tree, with values 9 and 15 respectively. Return 24.

## Solution - Recursive

``````class Solution {
public int sumOfLeftLeaves(TreeNode root) {
if (root == null) return 0;
int res = 0;
if (root.left != null) {
if (root.left.left == null && root.left.right == null) res += root.left.val;
else res += sumOfLeftLeaves(root.left);
}
res += sumOfLeftLeaves(root.right);
return res;
}
}``````

## Solution - Iterative

``````class Solution {
public int sumOfLeftLeaves(TreeNode root) {
if (root == null) return 0;
int res = 0;
Deque<TreeNode> stack = new ArrayDeque<>();
stack.push(root);
while (!stack.isEmpty()) {
TreeNode cur = stack.pop();
if (cur.left != null) {
if (cur.left.left == null && cur.left.right == null) {
res += cur.left.val;
} else {
stack.push(cur.left);
}
}
if (cur.right != null) {
if (cur.right.left != null || cur.right.right != null) {
stack.push(cur.right);
}
}
}
return res;
}
}``````