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---
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:
< ul >
< li > quarters (25 cents)< / li >
< li > dimes (10 cents)< / li >
< li > nickels (5 cents), and< / li >
< li > pennies (1 cent)< / li >
< / ul >
< p > There are six ways to make change for 15 cents:< / p >
< ul >
< li > A dime and a nickel< / li >
< li > A dime and 5 pennies< / li >
< li > 3 nickels< / li >
< li > 2 nickels and 5 pennies< / li >
< li > A nickel and 10 pennies< / li >
< li > 15 pennies< / li >
< / ul >
# --instructions--
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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.
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# --hints--
`countCoins` should be a function.
```js
assert(typeof countCoins === 'function');
```
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`countCoins(15)` should return `6` .
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```js
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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);
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```
# --seed--
## --seed-contents--
```js
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function countCoins(cents) {
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return true;
}
```
# --solutions--
```js
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function countCoins(cents) {
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const operands = [1, 5, 10, 25];
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const targetsLength = cents + 1;
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const operandsLength = operands.length;
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const t = [1];
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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];
}
```