#yyds干货盘点# LeetCode程序员面试金典：左叶子之和

class Solution {
    public int sumOfLeftLeaves(TreeNode root) {
        return root != null ? dfs(root) : 0;
    }

    public int dfs(TreeNode node) {
        int ans = 0;
        if (node.left != null) {
            ans += isLeafNode(node.left) ? node.left.val : dfs(node.left);
        }
        if (node.right != null && !isLeafNode(node.right)) {
            ans +=服务器托管网 dfs(node.right);
        }
        return ans;
    }

    public boolean isLeafNode(TreeNode node) {
        return node.lef服务器托管网t == null && node.right == null;
    }
}