0198-house-robber.js

/**
 * Brute Force - DFS
 * Time O(2^N) | Space O(N)
 * https://leetcode.com/problems/house-robber/
 * @param {number[]} nums
 * @return {number}
 */
var rob = (nums, i = 0) => {
    const isBaseCase = nums <= i;
    if (isBaseCase) return 0;

    const [ next, nextNext ] = [ (i + 1), (i + 2) ];
    const right = nums[i];
    const mid = rob(nums, next);     /* Time O(2^N) | Space O(N) */
    const left = rob(nums, nextNext);/* Time O(2^N) | Space O(N) */
    const house = left + right;

    return Math.max(house, mid);
};

/**
 * DP - Top Down
 * Array - Memoization
 * Time O(N) | Space O(N)
 * https://leetcode.com/problems/house-robber/
 * @param {number[]} nums
 * @return {number}
 */
var rob = (nums, i = 0, memo = initMemo(nums)) => {
    const isBaseCase = nums.length <= i;
    if (isBaseCase) return 0;

    const hasSeen = 0 <= memo[i];
    if (hasSeen) return memo[i];

    const [ next, nextNext ] = [ (i + 1), (i + 2) ];
    const right = nums[i];
    const mid = rob(nums, next, memo);     /* Time O(N) | Space O(N) */
    const left = rob(nums, nextNext, memo);/* Time O(N) | Space O(N) */
    const house = left + right;

    memo[i] = Math.max(mid, house);        /*           | Space O(N) */

    return memo[i];
};

const initMemo = (nums) => Array(nums.length + 1).fill(-1);

/**
 * DP - Bottom Up
 * Array - Tabulation
 * Time O(N) | Space O(N)
 * https://leetcode.com/problems/house-robber/
 * @param {number[]} nums
 * @return {number}
 */
var rob = (nums) => {
    if (!nums.length) return 0;

    const tabu = initTabu(nums);

    for (let i = 1; i < nums.length; i++) {/* Time O(N) */
        const right = nums[i];
        const mid = tabu[i];
        const left = tabu[i - 1];
        const house = left + right;

        tabu[i + 1] = Math.max(mid, house);       /* Space O(N) */
    }

    return tabu[nums.length]
};

const initTabu = (nums) => {
    const tabu = Array(nums.length + 1).fill(0);

    tabu[1] = nums[0];

    return tabu;
}

/**
 * DP - Bottom Up
 * Time O(N) | Space O(1)
 * https://leetcode.com/problems/house-robber/
 * @param {number[]} nums
 * @return {number}
 */
var rob = (nums) => {
    if (!nums.length) return 0;

    let [ left, mid ] = [ 0, 0 ];

    for (const right of nums) {/* Time O(N) */
        const temp = mid;
        const house = left + right;

        mid = Math.max(mid, house);
        left = temp;
    }

    return mid;
};