House Robber II

题目
You are a professional robber planning to rob houses along a street. Each house has a certain amount of money stashed. All houses at this place are arranged in a circle. That means the first house is the neighbor of the last one. Meanwhile, 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.

答案

class Solution {
    public int rob_sequence(int[] nums) {
        int n = nums.length;
        if(n == 0) return 0;
        // Define f[i][0] to mean: max number of coins we can steal from house i...n-1 (if we don't steal from i)
        // Define f[i][1] to mean: max number of coins we can steal from house i...n-1 (if we steal from i)
        
        int[][] f = new int[n][2];
        f[n - 1][0] = 0;
        f[n - 1][1] = nums[n - 1];
        
        for(int i = n - 2; i >= 0; i--) {
            f[i][0] = Math.max(f[i + 1][0], f[i + 1][1]);
            f[i][1] = f[i + 1][0] + nums[i];
        }
        return Math.max(f[0][0], f[0][1]);
    }
    
    public int rob(int[] nums) {
        int n = nums.length;
        if(n == 0) return 0;
        if(n == 1) return nums[0];
        
        
        int[] A = new int[n - 1];
        for(int i = 0; i < n - 1; i++) A[i] = nums[i];
        int ret1 = rob_sequence(A);
        
        for(int i = 1; i < n; i++) A[i - 1] = nums[i];
        int ret2 = rob_sequence(A);
        return Math.max(ret1, ret2);
    }
}