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.
Solution:
/**
* Definition for a binary tree node.
* public class TreeNode {
* int val;
* TreeNode left;
* TreeNode right;
* TreeNode() {}
* TreeNode(int val) { this.val = val; }
* TreeNode(int val, TreeNode left, TreeNode right) {
* this.val = val;
* this.left = left;
* this.right = right;
* }
* }
*/
class Solution {
public int sumOfLeftLeaves(TreeNode root) {
return helper(root, null);
}
private int helper(TreeNode root, TreeNode parent) {
if (root == null) return 0;
if (root.left == null && root.right == null && parent != null && parent.left == root) return root.val;
int left = helper(root.left, root);
int right = helper(root.right, root);
return left + right;
}
}