题目

代码

/**
 * 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 sum=0;
    public int sumOfLeftLeaves(TreeNode root) {
        if(root==null)
        return 0;
        if(leaf(root.left))
        return root.left.val+sumOfLeftLeaves(root.right);
        return sumOfLeftLeaves(root.right)+sumOfLeftLeaves(root.left);

    }
    public boolean leaf(TreeNode node)
    {
        if(node==null)
        return false;
        return node.left==null&&node.right==null;
    }
}

反思

1、认真看题，我就看错了，看成求左节点和