leetcode 213. House Robber II

leetcode 213. House Robber II

Note: This is an extension of House Robber.

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

 

本题是上一题的扩展，其实就是说第一个和第二个二选一的问题，那么算两次，一次为不选最后一个的时候，一次为不选第一个的时候为多少，最后选最大的

 

public class Solution {
    public int rob(int[] nums) {
        int n=nums.length;
        if (n==0){
            return 0;
        }
        if (n==1) return nums[0];
        if (n==2) return Math.max(nums[0], nums[1]);
        return Math.max(rob_helper(nums,0,n-1),rob_helper(nums,1,n));
    }

    public int rob_helper(int[] nums,int begin,int end) {
        int max=nums[begin];
        int max2=0;
        for (int i=1+begin;i<end;i++){
            if (nums[i]+max2>max){
                int tempmax2=max2;
                max2=max;
                max=nums[i]+tempmax2;
            }else {
                max2=max;
            }
        }
        return max;
    }
}