sumOfLeftLeaves.java

// 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 {

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

}