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