404. Sum of Left Leaves

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.

 private int sum;

        public int SumOfLeftLeaves(TreeNode root)
        {
            Chuck(root, false);
            return sum;
        }

        private void Chuck(TreeNode node, bool isLeft)
        {
            if (node == null)
            {
                return;
            }
            if (node.left == null && node.right == null)//leaf node
            {
                if (isLeft)
                {
                    sum = sum + node.val;
                }
            }
            else
            {
                Chuck(node.left, true);
                Chuck(node.right, false);
            }
        }

Runtime: 92 ms, faster than 98.11% of C# online submissions for Sum of Left Leaves.

Memory Usage: 22.7 MB, less than 5.16% of C# online submissions forSum of Left Leaves.