---
id: 59713bd26bdeb8a594fb9413
title: Count the coins
challengeType: 5
forumTopicId: 302238
dashedName: count-the-coins
---
# --description--
There are four types of common coins in [US](https://en.wikipedia.org/wiki/United_States) 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
# --instructions--
Implement a function to determine how many ways there are to make change for a given input, `cents`, that represents an amount of US pennies using these common coins.
# --hints--
`countCoins` should be a function.
```js
assert(typeof countCoins === 'function');
```
`countCoins(15)` should return `6`.
```js
assert.equal(countCoins(15), 6);
```
`countCoins(85)` shouls return `163`.
```js
assert.equal(countCoins(85), 163);
```
`countCoins(100)` should return `242`.
```js
assert.equal(countCoins(100), 242);
```
# --seed--
## --seed-contents--
```js
function countCoins(cents) {
return true;
}
```
# --solutions--
```js
function countCoins(cents) {
const operands = [1, 5, 10, 25];
const targetsLength = cents + 1;
const operandsLength = operands.length;
const 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];
}
```