2.0 KiB
2.0 KiB
title | id | challengeType |
---|---|---|
Count the coins | 59713bd26bdeb8a594fb9413 | 5 |
Description
There are four types of common coins in US currency:
quarters (25 cents) dimes (10 cents) nickels (5 cents), and pennies (1 cent)There are six ways to make change for 15 cents:
A dime and a nickel A dime and 5 pennies 3 nickels 2 nickels and 5 pennies A nickel and 10 pennies 15 pennies Task:Implement a function to determine how many ways there are to make change for a dollar using these common coins? (1 dollar = 100 cents).
Reference: an algorithm from MIT Press.Instructions
Tests
tests:
- text: <code>countCoins</code> is a function.
testString: assert(typeof countCoins === 'function', '<code>countCoins</code> is a function.');
- text: <code>countCoints()</code> should return 242.
testString: assert.equal(countCoins(), 242, '<code>countCoints()</code> should return 242.');
Challenge Seed
function countCoins () {
// Good luck!
return true;
}
Solution
function countCoins () {
let t = 100;
const operands = [1, 5, 10, 25];
const targetsLength = t + 1;
const operandsLength = operands.length;
t = [1];
for (let a = 0; a < operandsLength; a++) {
for (let b = 1; b < targetsLength; b++) {
// initialise undefined target
t[b] = t[b] ? t[b] : 0;
// accumulate target + operand ways
t[b] += (b < operands[a]) ? 0 : t[b - operands[a]];
}
}
return t[targetsLength - 1];
}