Leetcode Nested List Weight Sum

Given a nested list of integers, return the sum of all integers in the list weighted by their depth.

Each element is either an integer, or a list -- whose elements may also be integers or other lists.

Example 1:
Given the list [[1,1],2,[1,1]], return 10. (four 1's at depth 2, one 2 at depth 1)

Example 2:
Given the list [1,[4,[6]]], return 27. (one 1 at depth 1, one 4 at depth 2, and one 6 at depth 3; 1 + 4*2 + 6*3 = 27)

Difficulty: Easy

Solution: Recursion.

/** * // This is the interface that allows for creating nested lists. * // You should not implement it, or speculate about its implementation * public interface NestedInteger { * *     // @return true if this NestedInteger holds a single integer, rather than a nested list. *     public boolean isInteger(); * *     // @return the single integer that this NestedInteger holds, if it holds a single integer *     // Return null if this NestedInteger holds a nested list *     public Integer getInteger(); * *     // @return the nested list that this NestedInteger holds, if it holds a nested list *     // Return null if this NestedInteger holds a single integer *     public List<NestedInteger> getList(); * } */public class Solution {    public int helper(List<NestedInteger> nums, int dep){        int ans = 0;        for(int i = 0; i < nums.size(); i++){            if(nums.get(i).isInteger() == true){                ans += (nums.get(i).getInteger() * dep);            }            else{                ans += helper(nums.get(i).getList(), dep + 1);            }        }        return ans;    }    public int depthSum(List<NestedInteger> nestedList) {        return helper(nestedList, 1);    }}