# [LeetCode] 213. House Robber II 打家劫舍之二

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.

Example 1:

Input: [2,3,2]
Output: 3
Explanation: You cannot rob house 1 (money = 2) and then rob house 3 (money = 2),


Example 2:

Input: [1,2,3,1]
Output: 4
Explanation: Rob house 1 (money = 1) and then rob house 3 (money = 3).
Total amount you can rob = 1 + 3 = 4.

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

class Solution {
public:
int rob(vector<int>& nums) {
if (nums.size() <= 1) return nums.empty() ? 0 : nums[0];
return max(rob(nums, 0, nums.size() - 1), rob(nums, 1, nums.size()));
}
int rob(vector<int> &nums, int left, int right) {
if (right - left <= 1) return nums[left];
vector<int> dp(right, 0);
dp[left] = nums[left];
dp[left + 1] = max(nums[left], nums[left + 1]);
for (int i = left + 2; i < right; ++i) {
dp[i] = max(nums[i] + dp[i - 2], dp[i - 1]);
}
return dp.back();
}
};

class Solution {
public:
int rob(vector<int>& nums) {
if (nums.size() <= 1) return nums.empty() ? 0 : nums[0];
return max(rob(nums, 0, nums.size() - 1), rob(nums, 1, nums.size()));
}
int rob(vector<int> &nums, int left, int right) {
int robEven = 0, robOdd = 0;
for (int i = left; i < right; ++i) {
if (i % 2 == 0) {
robEven = max(robEven + nums[i], robOdd);
} else {
robOdd = max(robEven, robOdd + nums[i]);
}
}
return max(robEven, robOdd);
}
};

class Solution {
public:
int rob(vector<int>& nums) {
if (nums.size() <= 1) return nums.empty() ? 0 : nums[0];
return max(rob(nums, 0, nums.size() - 1), rob(nums, 1, nums.size()));
}
int rob(vector<int> &nums, int left, int right) {
int rob = 0, notRob = 0;
for (int i = left; i < right; ++i) {
int preRob = rob, preNotRob = notRob;
rob = preNotRob + nums[i];
notRob = max(preRob, preNotRob);
}
return max(rob, notRob);
}
};

Github 同步地址：

https://github.com/grandyang/leetcode/issues/213

House Robber

House Robber III

Paint House

Paint Fence

Non-negative Integers without Consecutive Ones

Coin Path

https://leetcode.com/problems/house-robber-ii/

https://leetcode.com/problems/house-robber-ii/discuss/59929/Java-clean-short-solution-DP

https://leetcode.com/problems/house-robber-ii/discuss/59934/Simple-AC-solution-in-Java-in-O(n)-with-explanation

LeetCode All in One 题目讲解汇总(持续更新中...)

posted @ 2015-05-21 03:26  Grandyang  阅读(...)  评论(... 编辑 收藏