打家劫舍（动态规划+滚动数组+取模运算优化）

    public static void main(String[] args) {
        int[] a =  {2,1,1,3};
        int[] b = {2,7,9,3,1};
        System.out.println(rob(a));
        System.out.println(rob(b));
    }
    public static  int rob(int[] nums) {
        int len = nums.length;
        if(len == 0)
            return 0;
        int[] dp = new int[len + 1];
        dp[0] = 0;
        dp[1] = nums[0];
        for(int i = 2; i <= len; i++) {
            dp[i] = Math.max(dp[i-1], dp[i-2] + nums[i-1]);
        }
        return dp[len];
    }