Problem Solving: Do You Have Enough Change

Problem Statement

Given a total due and an array representing the amount of change in your pocket, determine whether or not you can pay for the item. The change will always be represented in the following order: quarters, dimes, nickels, pennies.

To illustrate: changeEnough([25, 20, 5, 0], 4.25) should yield true, since having 25 quarters, 20 dimes, 5 nickels and 0 pennies gives you 6.25 + 2 + .25 + 0 = 8.50.

changeEnough([2, 100, 0, 0], 14.11) ➞ false
changeEnough([0, 0, 20, 5], 0.75) ➞ true
changeEnough([30, 40, 20, 5], 12.55) ➞ true
changeEnough([10, 0, 0, 50], 3.85) ➞ false
changeEnough([1, 0, 5, 219], 19.99) ➞ false

🚨 If you would like to solve the problem, give it a try now. Do not read further. The next part provides you with a solution.

Solution

Using plain old javascript:

const changeEnough = (changeArray, moneyNeeded) => 25 * changeArray[0] + 10 * changeArray[1] + 5 * changeArray[2] + changeArray[3] >= moneyNeeded * 100;

or slightly more readable:

const changeEnough = (changeArray, moneyNeeded) => {
    const moneyInPocket = 25 * changeArray[0] + 10 * changeArray[1] + 5 * changeArray[2] + changeArray[3];
    return moneyInPocket >= moneyNeeded * 100;
}

or using destructuring of arrays:

const changeEnough = (changeArray, moneyNeeded) => {
    const [quarters, dimes, nickels, pennies] = changeArray;
    const moneyInPocket = quarters * .25 + dimes * .10 + nickels * .05 + pennies;
    return moneyInPocket >= moneyNeeded;
}