House Robber

You are a professional robber planning to rob houses along a street. Each house has a certain amount of money stashed, the only constraint stopping you from robbing each of them is that adjacent houses have security system connected and it will automatically contact the police if two adjacent houses were broken into on the same night.

Given a list of non-negative integers representing the amount of money of each house, determine the maximum amount of money you can rob tonight without alerting the police.

假设我们现在在第三间房子里，我们要比较第三间与第一间的和与第二间的大小。取大的那个作为下次比较的第二间，下次比较的第一间是这次的第二间。

class Solution(object):
    def rob(self, nums):
        """
        :type nums: List[int]
        :rtype: int
        """
        last, now = 0, 0
        for n in nums:
            last, now = now, max(last + n, now)
        return now