# Halo

A magic place for coding

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## Problem

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. At least one digit, followed by a dot '.'.
2. At least one digit, followed by a dot '.', followed by at least one digit.
3. A dot '.', followed by at least one digit.

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

1. (Optional) A sign character (either '+' or '-').
2. At least one digit.

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:

Example 2:

Example 3:

Example 4:

Constraints:

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

## Analysis

这道题目要求我们验证给出的字符串是否一个合法的数字，这种题目考查的主要是各种 case 的判断。这道题目的情况实在是有点多，而且 test case 很复杂，直接参考 LeetCode Valid Number

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## Summary

这道题目的分享到这里，感谢你的支持！

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