*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)

 

 

/**
 * // 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 depthSum(List<NestedInteger> nestedList) {
        int sum = 0;
        int level = 1;
        while(nestedList.size()!=0)
        {
            List<NestedInteger> list = new LinkedList<NestedInteger>();
            for(int i=0;i<nestedList.size();i++)
            {
               if(nestedList.get(i).isInteger())
               {
                   sum = sum + nestedList.get(i).getInteger()*level;
               }
               else
               {
                   list.addAll(nestedList.get(i).getList());
               }
            }
            level++;
            nestedList = list;
        }
        
        return sum;
    }
}

 addAll() method: 

http://beginnersbook.com/2013/12/java-arraylist-addall-int-index-collection-c-method-example/