How should I practice Restricted Decimal Number Validator?

Start by reading the full statement, solve the visible examples, then compare the pattern against related LinkedIn phone screen problems in FastPrep.

Is Restricted Decimal Number Validator associated with LinkedIn?

FastPrep tags this as a LinkedIn phone screen coding practice problem when the problem catalog has that company and stage context.

LinkedIn● EasyNEW GRADPHONE SCREEN

You are given a string toTest. Return true exactly when it represents a number in the restricted decimal grammar below.

An optional minus sign - may appear only as the first character.
At least one ASCII digit must follow the optional sign.
An optional decimal point . may appear at most once, and it must have at least one digit on each side.
No other characters, whitespace, exponent notation, or leading plus sign are accepted.

Leading zeros are allowed.

isNumber(toTest: String) → boolean

toTest = "234"return = true

Every character is an ASCII digit.

toTest = "-455"return = true

A single leading minus sign is allowed.

toTest = "1e2"return = false

Exponent notation is outside the accepted decimal grammar.

toTest = "12^2"return = false

The caret is not a digit or the optional decimal point.

toTest = "23.23"return = true

There are digits on both sides of the only decimal point.

toTest = "2.2.4"return = false

A valid representation may contain at most one decimal point.