0322-coin-change.js

/**
 * Brute Force - DFS
 * Time O(S^N) | Space O(N)
 * https://leetcode.com/problems/coin-change/
 * @param {number[]} coins
 * @param {number} amount
 * @return {number}
 */
var coinChange = (coins, amount, coin = 0) => {
    const isBaseCase1 = amount === 0;
    if (isBaseCase1) return 0;

    const isBaseCase2 = !(coin < coins.length && 0 < amount);
    if (isBaseCase2) return -1;

    return dfs(coins, amount, coin); /* Time O(S^N) | Space O(N) */
};

var dfs = (coins, amount, coin) => {
    let [max, minCost] = [amount / coins[coin], Infinity];

    for (let num = 0; num <= max; num++) {
        /* Time O(N) */
        const caUpdate = num * coins[coin] <= amount;
        if (!caUpdate) continue;

        const product = num * coins[coin];
        const difference = amount - product;
        const min = coinChange(
            coins,
            difference,
            coin + 1,
        ); /* Time O(S^N) | Space O(N) */
        const cost = min + num;

        const isSentinel = min === -1;
        if (isSentinel) continue;

        minCost = Math.min(minCost, cost);
    }

    return minCost !== Infinity ? minCost : -1;
};

/**
 * DP - Top Down
 * Array - Memoization
 * Time O(N) | Space O(N)
 * https://leetcode.com/problems/coin-change/
 * @param {number[]} coins
 * @param {number} amount
 * @return {number}
 */
var coinChange = (coins, amount, memo = initMemo(amount)) => {
    const isBaseCase1 = amount < 0;
    if (isBaseCase1) return -1;

    const isBaseCase2 = amount < 1;
    if (isBaseCase2) return 0;

    const isBaseCase3 = memo[amount - 1] !== 0;
    if (isBaseCase3) return memo[amount - 1];

    return dfs(coins, amount, memo); /* Time O(N) | Space O(N) */
};

const initMemo = (amount) => Array(amount).fill(0);

var dfs = (coins, amount, memo, min = Infinity) => {
    for (const coin of coins) {
        /* Time O(N) */
        const cost = coinChange(
            coins,
            amount - coin,
            memo,
        ); /* Time O(N) | Space O(N) */

        const canUpdate = 0 <= cost && cost < min;
        if (!canUpdate) continue;

        min = cost + 1;
    }

    memo[amount - 1] = min !== Infinity ? min : -1;

    return memo[amount - 1];
};

/**
 * DP - Bottom Up
 * Array - Tabulation
 * Time O(N) | Space O(N)
 * https://leetcode.com/problems/coin-change/
 * @param {number[]} coins
 * @param {number} amount
 * @return {number}
 */
var coinChange = (coins, amount) => {
    const tabu = initTabu(amount);

    for (let _amount = 1; _amount <= amount; _amount++) {
        /* Time O(N) */
        for (let coin = 0; coin < coins.length; coin++) {
            /* Time O(N) */
            const canUpdate = coins[coin] <= _amount;
            if (!canUpdate) continue;

            const difference = _amount - coins[coin];
            const min = tabu[difference] + 1;

            tabu[_amount] = Math.min(tabu[_amount], min); /* Space O(N) */
        }
    }

    return tabu[amount] <= amount ? tabu[amount] : -1;
};

const initTabu = (amount) => {
    const tabu = Array(amount + 1).fill(amount + 1);

    tabu[0] = 0;

    return tabu;
};