LeetCode in Python 339. Nested List Weight Sum

时间:2019-07-11
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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
# """
# class NestedInteger(object):
# def isInteger(self):
# """
# @return True if this NestedInteger holds a single integer, rather than a nested list.
# :rtype bool
# """
#
# def getInteger(self):
# """
# @return the single integer that this NestedInteger holds, if it holds a single integer
# Return None if this NestedInteger holds a nested list
# :rtype int
# """
#
# def getList(self):
# """
# @return the nested list that this NestedInteger holds, if it holds a nested list
# Return None if this NestedInteger holds a single integer
# :rtype List[NestedInteger]
# """

class Solution(object):
    def weightSum(self, nestedList, curLevel=1):
        """
        :type nestedList: List[NestedInteger]
        :rtype: int
        """
        sum = 0
        for element in nestedList:
            if element.isInteger():
                sum += curLevel*element.getInteger()
            else:
                sum += weightSum(element.getList(), curLevel+1)
        return sum

注意curLevel从1开始,典型DFS,for循环中递归调用函数

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