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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.
1import java.util.regex.Pattern;
2import java.util.regex.Matcher;
3
4public class ValidNumber {
5 public static boolean isNumber(String s) {
6 Pattern pattern = Pattern.compile("^[\+-]?(\d+\.?|\.\d)\d*([eE][\+-]?\d+)?$");
7 Matcher matcher = pattern.matcher(s);
8 return matcher.matches();
9 }
10 public static void main(String[] args) {
11 System.out.println(isNumber("53.5e93")); // true
12 System.out.println(isNumber("1a")); // false
13 }
14}Java’s regex API is used here for efficient pattern matching. This allows specifying valid number formats including integers, decimals, and numbers with exponents.
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.
1def
This Python approach iterates through the string, ensuring all rules for a valid number are adhered to based on the position and current context of each character.