83 lines
1.5 KiB
Markdown
83 lines
1.5 KiB
Markdown
---
|
|
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--
|
|
|
|
Implement a function to determine how many ways there are to make change for a dollar using these common coins (1 dollar = 100 cents)
|
|
|
|
# --hints--
|
|
|
|
`countCoins` should be a function.
|
|
|
|
```js
|
|
assert(typeof countCoins === 'function');
|
|
```
|
|
|
|
`countCoins()` should return 242.
|
|
|
|
```js
|
|
assert.equal(countCoins(), 242);
|
|
```
|
|
|
|
# --seed--
|
|
|
|
## --seed-contents--
|
|
|
|
```js
|
|
function countCoins() {
|
|
|
|
return true;
|
|
}
|
|
```
|
|
|
|
# --solutions--
|
|
|
|
```js
|
|
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];
|
|
}
|
|
```
|