198. House Robber

Description

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.

Constraints

• 0 <= nums.length <= 100

• 0 <= nums[i] <= 400

Approach

Links

• GeeksforGeeks

• Leetcode

• ProgramCreek

• YouTube

Examples

Example 1

Input: nums = [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: nums = [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.

Solutions

Solution 1

/**
 * Time complexity : O(N)
 * Space complexity : O(1)
 */

class Solution {
    public int rob(int[] nums) {
        int prevToPrev = 0;
        int prev = 0;
        int max = 0;
        
        for(int n: nums) {
            max = Math.max(prev, prevToPrev+n);
            prevToPrev = prev;
            prev = max;
        }
        
        return max;
    }
}

Solution 2

/**
 * Time complexity : O(N)
 * Space complexity : O(1)
 */
 
 class Solution {
    public int rob(int[] nums) {
        int prevMax = 0;
        int currMax = 0;
        
        for(int num: nums) {
            int tmp = currMax;
            currMax = Math.max(currMax, prevMax+num);
            prevMax = tmp;
        }
        
        return currMax;
    }
}

Follow up