404. Sum of Left Leaves

    没有什么好说的，求二叉树所有左叶子节点的值

/**
 * 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 sum = 0;
        if (root.left != null && root.left.left == null && root.left.right == null) {
            sum += root.left.val;
        } else {
            sum += sumOfLeftLeaves(root.left);
        }
        sum += sumOfLeftLeaves(root.right);
        return sum;
    }
}