# 198. House Robber

You are a professional robber planning to rob houses along a street. Each house has a certain amount of money stashed, the only constraint stopping you from robbing each of them is that 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: [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.

Example 2:

Input: [2,7,9,3,1]
Output: 12
Explanation: Rob house 1 (money = 2), rob house 3 (money = 9) and rob house 5 (money = 1).
             Total amount you can rob = 2 + 9 + 1 = 12.

# Solution

Approach 1: Dynamic programming.

# Code (Python)

Approach 1:

    def rob(self, nums: List[int]) -> int:
        if not nums:
            return 0
        if len(nums) < 3:
            return max(nums)
        # table[i] = max(table[i-1],table[i-2]+nums[i])
        prev, current = nums[0], max(nums[0], nums[1])
        for i in range(2, len(nums)):
            new_current = max(current, nums[i] + prev)
            prev, current = current, new_current
        return current

# Code (C++)

Approach 1:

class Solution {
public:
    int rob(vector<int>& nums) {
        int numsSize = nums.size();
        if (numsSize == 0) return 0;
        int value[numsSize][2];
        value[0][0] = 0;
        value[0][1] = nums[0];
        for (int i = 1; i < numsSize; ++i)
        {
            value[i][0] = std::max(value[i-1][0], value[i-1][1]);
            value[i][1] = value[i-1][0] + nums[i];
        }
        return std::max(value[numsSize-1][0], value[numsSize-1][1]);
    }
};

class Solution {
public:
    int rob(vector<int>& nums) {
        int prev0 = 0;
        int prev1 = 0;
        for (int i = 0; i < nums.size(); ++i)
        {
            int curr0 = std::max(prev0, prev1);
            int curr1 = prev0 + nums[i];
            prev0 = curr0;
            prev1 = curr1;
        }
        return std::max(prev0, prev1);
    }
};

class Solution {
public:
    int rob(vector<int>& nums) {
        int prev = 0;
        int prevPrev = 0;
        for (int i = 0; i < nums.size(); ++i)
        {
            int curr = std::max(prev, prevPrev + nums[i]);
            prevPrev = prev;
            prev = curr;
        }
        return prev;
    }
};