leetcode404: Sum of Left Leaves

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.

public int sumOfLeftLeaves(TreeNode root) {if (root == null)return 0;if (root.left != null && root.left.left == null && root.left.right == null)return root.left.val + sumOfLeftLeaves(root.right);return sumOfLeftLeaves(root.left) + sumOfLeftLeaves(root.right);}