LeetCode 339. Nested List Weight Sum

https://leetcode.com/problems/nested-list-weight-sum/submissions/

Example 1:

Input: [[1,1],2,[1,1]]
Output: 10 
Explanation: Four 1's at depth 2, one 2 at depth 1.

Example 2:

Input: [1,[4,[6]]]
Output: 27 
Explanation: One 1 at depth 1, one 4 at depth 2, and one 6 at depth 3; 1 + 4*2 + 6*3 = 27.

	/**
	* // This is the interface that allows for creating nested lists.
	* // You should not implement it, or speculate about its implementation
	* public interface NestedInteger {
	* // Constructor initializes an empty nested list.
	* public NestedInteger();
	*
	* // Constructor initializes a single integer.
	* public NestedInteger(int value);
	*
	* // @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();
	*
	* // Set this NestedInteger to hold a single integer.
	* public void setInteger(int value);
	*
	* // Set this NestedInteger to hold a nested list and adds a nested integer to it.
	* public void add(NestedInteger ni);
	*
	* // @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();
	* }
	*/
	class Solution {
	public int depthSum(List<NestedInteger> nestedList) {
	// handle corner case inputs
	if (nestedList == null || nestedList.size() == 0) {
	return 0;
	}
	// call DFS to solve this nested list recursivly
	return depthSum(nestedList, 1);
	}
	private int depthSum(List<NestedInteger> lst, int depth) {
	// handle corner case inputs
	if (lst == null || lst.size() == 0) {
	return 0;
	}
	int result = 0;
	for (NestedInteger entry: lst) {
	if (entry.isInteger()) {
	// a number!
	result += entry.getInteger() * depth;
	} else {
	// a nested list!
	result += depthSum(entry.getList(), depth + 1);
	}
	}
	return result;
	}
	}

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