43 lines
923 B
Markdown
43 lines
923 B
Markdown
|
---
|
||
|
id: 5900f3fd1000cf542c50ff10
|
||
|
title: 'Problem 145: How many reversible numbers are there below one-billion?'
|
||
|
challengeType: 5
|
||
|
forumTopicId: 301774
|
||
|
dashedName: problem-145-how-many-reversible-numbers-are-there-below-one-billion
|
||
|
---
|
||
|
|
||
|
# --description--
|
||
|
|
||
|
Some positive integers n have the property that the sum \[ n + reverse(n) ] consists entirely of odd (decimal) digits. For instance, 36 + 63 = 99 and 409 + 904 = 1313. We will call such numbers reversible; so 36, 63, 409, and 904 are reversible. Leading zeroes are not allowed in either n or reverse(n).
|
||
|
|
||
|
There are 120 reversible numbers below one-thousand.
|
||
|
|
||
|
How many reversible numbers are there below one-billion (109)?
|
||
|
|
||
|
# --hints--
|
||
|
|
||
|
`euler145()` should return 608720.
|
||
|
|
||
|
```js
|
||
|
assert.strictEqual(euler145(), 608720);
|
||
|
```
|
||
|
|
||
|
# --seed--
|
||
|
|
||
|
## --seed-contents--
|
||
|
|
||
|
```js
|
||
|
function euler145() {
|
||
|
|
||
|
return true;
|
||
|
}
|
||
|
|
||
|
euler145();
|
||
|
```
|
||
|
|
||
|
# --solutions--
|
||
|
|
||
|
```js
|
||
|
// solution required
|
||
|
```
|