QRegExp for validating a float entered ina lineEdit

[gt.beta2]

Hi,
I want to read a number in the rangue [0; 20] with one "decimal" precision.
Examples:
0
1.5
12.4
14
20

I'm using ...

...
QRegExp regExp("[0-9]{1,1}|1[0-9]{1,1}|20");
lineEdit_t1->setValidator(new QRegExpValidator(regExp, this));
...

...
QRegExp regExp("[0-9]{1,1}|1[0-9]{1,1}|20");
lineEdit_t1->setValidator(new QRegExpValidator(regExp, this));
...

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This validates integer only but is there a shorter way?
What if i want to extend it for the numbers in the example above?

I supose i could use input masks or something but i am trying the regular expressions.

Thanks