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A regular expression can be used to validate if a string is a valid number by matching patterns that define valid numbers. This pattern matches integers with optional signs, decimals, and scientific notation.
Time Complexity: O(n) due to scanning each character in the string.
Space Complexity: O(1) since we're using a fixed-size pattern.
1using System;
2using System.Text.RegularExpressions;
3
4class ValidNumber {
5 public static bool IsNumber(string s) {
6 string pattern = "^[\+-]?((\d+\.?|\.\d)\d*)([eE][\+-]?\d+)?$";
7 return Regex.IsMatch(s, pattern);
8 }
9 public static void Main() {
10 Console.WriteLine(IsNumber("53.5e93")); // True
11 Console.WriteLine(IsNumber("1a")); // False
12 }
13}This C# solution uses the Regex class which allows regex-based validation of the input string against number-like patterns.
This approach involves parsing the string based on its characters and their positions. By iterating through the string, the method confirms whether it forms a valid number pattern based on segment rules.
Time Complexity: O(n) where n is the length of the string.
Space Complexity: O(1) using variables to track state.
1public The Java solution involves iterating over the string and validating each character based on context and position. It utilizes a straightforward approach to enforce number parsing rules.