特别简单题；Linear time, constant space
public class Solution {
public int rob(int[] nums) {
if (nums == null || nums.length==0) return 0;
int n = nums.length;
if (n == 1) return nums[0];
if (n == 2) return Math.max(nums[0], nums[1]);
int two_house_before = nums[0], one_house_before = Math.max(nums[0], nums[1]), current_house = 0;
for (int i=2; i<n; i++) {
current_house = Math.max(one_house_before, two_house_before + nums[i]);
two_house_before = one_house_before;
one_house_before = current_house;
}
return current_house;
}
}
