LeetCode 1022.从根到叶的二进制之和（简单）

public class Solution {
    public int sumRootToLeaf(TreeNode root) {
        return dfs(root,0);
    }
    public int dfs(TreeNode root,int val){
        if(root==null){
            return 0;
        }
        val=(val<<1)|root.val;
        if(root.left==null&&root.right==null){
            return val;
        }
        return dfs(root.left,val) +dfs(root.right,val);
    }
}