213. House Robber II Java Solutions

After robbing those houses on that street, the thief has found himself a new place for his thievery so that he will not get too much attention. This time, all houses at this place are arranged in a circle. That means the first house is the neighbor of the last one. Meanwhile, the security system for these houses remain the same as for those in the previous street.

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.

Credits:
Special thanks to @Freezen for adding this problem and creating all test cases.

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public class Solution {
    public int rob(int[] nums) {
        if(nums == null || nums.length <1) return 0;
        if(nums.length == 1) return nums[0];
        if(nums.length == 2) return Math.max(nums[0],nums[1]);//将其分为两种情况：１.包括nums[0] 2.包括nums[nums.length-1]
        return Math.max(getRob(nums,0,nums.length-2), getRob(nums,1,nums.length-1));
    }
    
    public int getRob(int[] nums,int s,int e){
        int len = e - s + 1;
        int[] res = new int[len];
        res[0] = nums[s];
        res[1] = Math.max(nums[s],nums[s+1]);
        for(int i = 2;i<len;i++){
            res[i] = Math.max(res[i-2]+nums[s+i], res[i-1]);
        }
        return res[len-1];
    }
}