leetcode--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 tonightwithout alerting the police.

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1. public int rob(int[] nums) {  
2.         if(nums==null || nums.length==0) return 0;    
3.         if(nums.length==1) return nums[0];    
4.         if(nums.length==2) return Math.max(nums[0], nums[1]);    
5.         return Math.max(helper(nums, 0, nums.length-2), helper(nums, 1, nums.length-1));    
6.     }  
7.       
8.     public int helper(int[] nums,int start,int end){  
9.         int n = end-start+1;  
10.         if(n==0) return 0;  
11.         if(n==1) return nums[start];  
12.         int[] flag = new int[n];  
13.         flag[0] = nums[start];  
14.         flag[1] = Math.max(nums[start], nums[start+1]);       
15.         for(int i=start+2;i<=end;i++){  
16.             flag[i-start] = Math.max(flag[i-start-2]+nums[i],flag[i-start-1]);            
17.         }  
18.         return flag[n-1];  
19.     }  

原文链接http://blog.youkuaiyun.com/crazy__chen/article/details/46580553