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.

动态规划 若抢当前户，则前一户不能抢，成果为 两户以前的收益与当前户之和 若不抢当前户，则成果为一户以前的收益 两者取最大值

状态转移方程 f(n) = Max(f(n-2)+num[n], f(n-1))

如 1,3,5,4,2,6 n 0 1 2 3 4 5 f(n-2) 0 0 1 3 6 7 f(n-1) 0 1 3 6 7 8 f(n) 1 3 6 7 8 13 结果为13

又如 2,1,1,2 n 2 1 1 2 f(n-2) 0 0 2 2 f(n-1) 0 2 2 3 f(n) 2 2 3 4 结果为4