LintCode 392 House Robber

// Ref: https://segmentfault.com/a/1190000003811581
// Ref: http://www.cnblogs.com/grandyang/p/4383632.html

/*
如果选择了抢劫上一个屋子，那么就不能抢劫当前的屋子，所以最大收益就是抢劫上一个屋子的收益
如果选择抢劫当前屋子，就不能抢劫上一个屋子，所以最大收益是到上一个屋子的上一个屋子为止的最大收益，加上当前屋子里有的钱
*/

 public static long houseRobber(int[] A) {
         int len = A.length;
         if (len <= 1) {
             return len == 0 ? 0: A[0];
         }

         long previous = A[0]; // a is the previous max
         long current = Math.max(A[0], A[1]); // b is the current max
         for(int i = 2; i < len; i++){
             long tmp = current;
             // previous + A[i] => pre-pre + current
             // b/c it cannot rob adjacent houses => need to compare
             current = Math.max(previous + A[i], current);
             previous = tmp;
         }
         return current;
     }