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

Example:

3   / \  9  20    /  \   15   7There 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.