1022.从根到叶的二进制数之和.java

/*
 * @lc app=leetcode.cn id=1022 lang=java
 *
 * [1022] 从根到叶的二进制数之和
 */

// @lc code=start
/**
 * 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 sumRootToLeaf(TreeNode root) {
        return dfs(root, 0);
    }

    private int dfs(TreeNode node, int val) {
        if (node == null) {
            return 0;
        }
        val = (val << 1) + node.val;
        if (node.left == null && node.right == null) {
            return val;
        }
        return dfs(node.left, val) + dfs(node.right, val);
    }
}
// @lc code=end