# GeetCode Hub

A valid number can be split up into these components (in order):

1. A decimal number or an integer.
2. (Optional) An `'e'` or `'E'`, followed by an integer.

A decimal number can be split up into these components (in order):

1. (Optional) A sign character (either `'+'` or `'-'`).
2. One of the following formats:
1. One or more digits, followed by a dot `'.'`.
2. One or more digits, followed by a dot `'.'`, followed by one or more digits.
3. A dot `'.'`, followed by one or more digits.

An integer can be split up into these components (in order):

1. (Optional) A sign character (either `'+'` or `'-'`).
2. One or more digits.

For example, all the following are valid numbers: `["2", "0089", "-0.1", "+3.14", "4.", "-.9", "2e10", "-90E3", "3e+7", "+6e-1", "53.5e93", "-123.456e789"]`, while the following are not valid numbers: `["abc", "1a", "1e", "e3", "99e2.5", "--6", "-+3", "95a54e53"]`.

Given a string `s`, return `true` if `s` is a valid number.

Example 1:

```Input: s = "0"
Output: true
```

Example 2:

```Input: s = "e"
Output: false
```

Example 3:

```Input: s = "."
Output: false
```

Example 4:

```Input: s = ".1"
Output: true
```

Constraints:

• `1 <= s.length <= 20`
• `s` consists of only English letters (both uppercase and lowercase), digits (`0-9`), plus `'+'`, minus `'-'`, or dot `'.'`.

class Solution { public boolean isNumber(String s) { } }