I'm trying to write a regex to validate below conditions in a password string

* Atleast one number and a letter
* Should not contain any special characters

Tried this regex

```
[a-zA-Z]+[0-9]+[a-zA-Z0-9]*|[0-9]+[a-zA-Z][a-zA-Z0-9]*

```

But it allows special characters. 
Any help would be appreciated!

**Example**

* aaaa - Not accepted
* 11111 - Not accepted
* aaaa1 - Accepted
* aaaa1\* - Not accepted