/** * Definition for a binary tree node. * public class TreeNode { * int val; * TreeNode left; * TreeNode right; * TreeNode(int x) { val = x; } * } */ class Solution { public int sumOfLeftLeaves(TreeNode root) { return getSum(root, false); } private int getSum(TreeNode root, boolean isLeft) { if (root == null) { return 0; } if (root.left == null && root.right == null && isLeft) { return root.val; } return getSum(root.left, true) + getSum(root.right, false); } }