How to Solve the House Robber II Challenge in Java
The challenge
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 a 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 nums
representing the amount of money of each house, return the maximum amount of money you can rob tonight without alerting the police.
Example 1:
Example 2:
Example 3:
Constraints:
1 <= nums.length <= 100
0 <= nums[i] <= 1000
The solution in Java code
class Solution {
public int rob(int[] nums) {
if (nums.length ==1) return nums[0];
return Math.max(rob(nums, 0, nums.length-2), rob(nums, 1, nums.length-1));
}
private int rob(int[]nums, int start, int end) {
int a = 0, b = 0;
for (int i = start; i <= end; i++) {
int temp = b;
if (nums[i] + a > b) b = nums[i] + a;
a = temp;
}
return b;
}
}
An Alternate View at the Acceptance Criteria
If we take the first example and say that:
If we take this new viewpoint, then we can write the following code to resolve the problem:
class Solution {
public int rob(int[] nums) {
// start from 0, then skip until end, build a total
int total1 = 0;
// start from 1, then skip until end, build a total
int total2 = 0;
for (int i=0; i<=nums.length; i++) {
int val = (i==nums.length) ? 0 : nums[i];
if (i%2==0) total1 += val;
else total2 += val;
}
// compare the totals and give the higher one
return Math.max(total1, total2);
}
}