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.

Example 1:

Input: [1,2,3,1]Output: 4Explanation: Rob house 1 (money = 1) and then rob house 3 (money = 3).             Total amount you can rob = 1 + 3 = 4.

Example 2:

Input: [2,7,9,3,1]Output: 12Explanation: Rob house 1 (money = 2), rob house 3 (money = 9) and rob house 5 (money = 1).             Total amount you can rob = 2 + 9 + 1 = 12.

题目描述：抢劫一排住户，但是不能抢邻近的住户，求最大抢劫量。

定义 dp 数组用来存储最大的抢劫量，其中 dp[i] 表示抢到第 i 个住户时的最大抢劫量

自己第一想法：这个想法没有完全理解题意，没有考虑到 2,1,1,2这种有两个间隔的情况。

方法一：动态规划

动态规划的特点是：保留了子问题的解。

由于不能抢劫邻近住户，如果抢劫了第 i -1 个住户，那么就不能再抢劫第 i 个住户，所以