Sum of Left Leaves | Problems

You get the root of a binary tree. A leaf is a node with no children. A left leaf is a leaf that is the left child of its parent. Return the sum of the values of all left leaves. If there are none, the sum is 0.

Do not count right leaves. Do not count a node that has only a right child.

Example 1

Input: root = [3, 9, 20, null, null, 15, 7]
Output: 24 (left leaf 9 plus left leaf 15)

Example 2

Input: root = [1]
Output: 0 (the root is not a left child)

Constraints

The tree has between 1 and 1000 nodes
-1000 <= Node.val <= 1000

Sample Input

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Sample Output

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Constraints

1 <= number of nodes <= 1000
-1000 <= Node.val <= 1000

Topics

Tree Binary Tree DFS

DFS

function sumOfLeftLeaves(root) {
  if (!root) return 0;
  let sum = 0;
  if (root.left && !root.left.left && !root.left.right) sum += root.left.val;
  else sum += sumOfLeftLeaves(root.left);
  sum += sumOfLeftLeaves(root.right);
  return sum;
}

Time: O(n) | Space: O(h)

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