Given the root of a binary tree, return the sum of all left leaves.
A leaf is a node with no children. A left leaf is a leaf that is the left child of another node.
Input: root = [3,9,20,null,null,15,7]
Output: 24
Explanation: There are two left leaves in the binary tree,
with values 9 and 15 respectively.Input: root = [1]
Output: 0-1000 <= Node.val <= 1000- The number of nodes in the tree is in the range
[1, 1000].
const sumOfLeftLeaves = (root) => {
if (!root) return 0;
const {left, right} = root;
let [sumLeft, sumRight] = [sumOfLeftLeaves(left), sumOfLeftLeaves(right)];
if (!sumLeft && left && !left.left && !left.right) sumLeft = left.val;
return Number(sumLeft) + Number(sumRight);
};I've written a function called sumOfLeftLeaves that calculates the sum of the values of the left leaves in a binary tree.
If the root node is null, indicating an empty tree, the function immediately returns 0.
If the root node is not null, the function uses destructuring assignment to extract the left and right children of the root node.
The function then recursively calls itself on the left and right children, storing the returned values in the variables sumLeft and sumRight respectively.
Next, it checks if sumLeft is 0, which means there are no left leaves encountered yet. It also checks if the left child exists and is a leaf node, meaning it has no left or right child. If these conditions are met, the value of the leaf node is assigned to sumLeft.
Finally, the function returns the sum of sumLeft and sumRight, after converting them to numbers using the Number function.
In summary, this function recursively calculates the sum of the values of the left leaves in a binary tree. It traverses the tree, keeping track of the sum of the left leaves encountered so far, and returns the final sum.