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LeetCode 213. House Robber II (javascript solution)

Description:

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 an integer array nums representing the amount of money of each house, return the maximum amount of money you can rob tonight without alerting the police.

Solution:

Time Complexity : O(n)
Space Complexity: O(n)

var rob = function(nums) {
    // Handle base case
    if(!nums.length) return 0
    if(nums.length===1) return nums[0]
    if(nums.length===2) return Math.max(nums[0], nums[1])

    // Return the max between the subarray if we starting robbing at the first house or if we started robbing at the second house
    return Math.max(helper(nums.slice(0, nums.length-1)), helper(nums.slice(1)))
};

// Helper function follows same logic as house rober 1
function helper(segment) {
    if(!segment.length) return 0
    if(segment.length===1) return segment[0]
    if(segment.length===2) return Math.max(segment[0], segment[1])
    const dp = [segment[0], Math.max(segment[0], segment[1])]
    for(let i = 2; i < segment.length; i++) {
        dp[i] = Math.max(segment[i]+dp[i-2], dp[i-1])
    }
    return dp[dp.length-1]
}

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