364. Nested List Weight Sum II

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.

Different from theprevious questionwhere weight is increasing from root to leaf, now the weight is defined from bottom up. i.e., the leaf level integers have weight 1, and the root level integers have the largest weight.

Example 1:
Given the list[[1,1],2,[1,1]], return8. (four 1's at depth 1, one 2 at depth 2)
Example 2:
Given the list[1,[4,[6]]], return17. (one 1 at depth 3, one 4 at depth 2, and one 6 at depth 1; 1*3 + 4*2 + 6*1 = 17)

借助一个临时的arraylist 倒腾数据， 不需要计算权， 外层循环往上加， 一直加到最内层。