32 lines
510 B
Markdown
32 lines
510 B
Markdown
|
---
|
||
|
|
title: Left factorials
|
||
|
|
---
|
||
|
|
# Left factorials
|
||
|
|
|
||
|
|
---
|
||
|
|
## Solutions
|
||
|
|
|
||
|
|
<details><summary>Solution 1 (Click to Show/Hide)</summary>
|
||
|
|
|
||
|
|
```javascript
|
||
|
|
function leftFactorial(n) {
|
||
|
|
if (n == 0)
|
||
|
|
return 0
|
||
|
|
if (n == 1)
|
||
|
|
return 1;
|
||
|
|
|
||
|
|
// Note: for n>=20, the result may not be correct.
|
||
|
|
// This is because JavaScript uses 53 bit integers and
|
||
|
|
// for n>=20 result becomes too large.
|
||
|
|
|
||
|
|
let res = 2, fact = 2;
|
||
|
|
for (var i = 2; i < n; i++) {
|
||
|
|
res += fact;
|
||
|
|
fact *= (i + 1);
|
||
|
|
}
|
||
|
|
|
||
|
|
return res;
|
||
|
|
}
|
||
|
|
```
|
||
|
|
|
||
|
|
</details>
|