How to validate Indian Passport number using Regular Expression

Given a string str of alphanumeric characters, the task is to check whether the given string is a valid passport number or not by using Regular Expression. 

A valid passport number in India must satisfy the following conditions: 

1. It should be eight characters long.
2. The first character should be an uppercase alphabet.
3. The next two characters should be a number, but the first character should be any number from 1-9 and the second character should be any number from 0-9.
4. It should be zero or one white space character.
5. The next four characters should be any number from 0-9.
6. The last character should be any number from 1-9.

Exapmles:

Input: str = "A2096457";  Output: true  Explanation: The given string satisfies all the above mentioned conditions. Therefore it is a valid passport number of India. Input: str = "12096457";  Output: false  Explanation: The given string doesn't starts with an upper case alphabet. Therefore it is not a valid passport number of India. Input: str = "A209645704";  Output: false  Explanation: The given string contains 10 characters. Therefore it is not a valid passport number of India.

Approach:

The idea is to use Regular Expression to solve this problem. The following steps can be followed to compute the answer. 

1. Get the String.
2. Create a regular expression to check valid passport number of India as mentioned below: 

• regex = "^[A-Z][1-9]\d\s?\d{4}[1-9]$" Where:  ^: Asserts the position at the start of the string.
• [A-Z]: Ensures the first character is an uppercase letter from A to Z, which includes Q and X (since these are not excluded in your revised requirement).
• [1-9]: The second character must be a digit from 1 to 9.
• \d: The third character can be any digit from 0 to 9.
• \s?: There can be zero or one whitespace character.
• \d{4}: The next four characters must be digits from 0 to 9.
• [1-9]: The last character must be a digit from 1 to 9.
• $: Asserts the position at the end of the string.

1. Match the given string with the Regular Expression. In Java, this can be done by using Pattern.matcher().
2. Return true if the string matches with the given regular expression, else return false.

Below is the implementation of the above approach:

#include <iostream>
#include <regex>
using namespace std;

// Function to validate the passport number
bool isValidPassportNo(const string& str) {
    // Regex to check valid passport number
    const regex pattern("^[A-Z][1-9]\\d\\s?\\d{4}[1-9]$");

    // Return false if the passport number is empty
    if (str.empty()) {
        return false;
    }

    // Return true if the passport number matches the regex pattern
    return regex_match(str, pattern);
}

// Driver Code
int main() {
    // Test Case 1:
    
    string str1 = "A21 90457";
    cout << (isValidPassportNo(str1) ? "true" : "false") << endl;

    // Test Case 2:
   
    string str2 = "A0296457";
    cout << (isValidPassportNo(str2) ? "true" : "false") << endl;

    // Test Case 3:
 
    string str3 = "Q2096453"; 
    cout << (isValidPassportNo(str3) ? "true" : "false") << endl;

    // Test Case 4:
 
    string str4 = "12096457"; 
    cout << (isValidPassportNo(str4) ? "true" : "false") << endl;

    // Test Case 5:
    
    string str5 = "A209645704";
    cout << (isValidPassportNo(str5) ? "true" : "false") << endl;

    return 0;
}

import java.util.regex.Pattern;
import java.util.regex.Matcher;

public class PassportValidator {

    // Function to validate the passport number
    public static boolean isValidPassportNo(String str) {
        // Regex to check valid passport number
        // The pattern ensures:
        // - Starts with an uppercase letter (A-Z)
        // - Followed by a digit between 1-9
        // - Followed by any digit (0-9)
        // - Optional single whitespace
        // - Followed by exactly four digits (0-9)
        // - Ends with a digit between 1-9
        String regex = "^[A-Z][1-9]\\d\\s?\\d{4}[1-9]$";
        Pattern pattern = Pattern.compile(regex);
        Matcher matcher = pattern.matcher(str);

        // Return true if the passport number matches the regex
        return matcher.matches();
    }

    public static void main(String[] args) {
        // Test Case 1:
        // Valid format (starts with an uppercase letter, correct length, optional space, ends with a digit)
        String str1 = "A21 90457";
    
        System.out.println(isValidPassportNo(str1));

        // Test Case 2:
        // Valid format (starts with an uppercase letter, correct length, no space, ends with a digit)
        String str2 = "A0296457";
    
        System.out.println(isValidPassportNo(str2));

        // Test Case 3:
        // Valid format (starts with an uppercase letter, correct length, no space, ends with a digit)
        String str3 = "Q2096453";
       
        System.out.println(isValidPassportNo(str3));

        // Test Case 4:
        // Invalid (does not start with an uppercase letter)
        String str4 = "12096457";
    
        System.out.println(isValidPassportNo(str4));

        // Test Case 5:
        // Invalid (length is not 8 characters)
        String str5 = "A209645704";
    
        System.out.println(isValidPassportNo(str5));
    }
}

import re

def is_valid_passport_no(s):
    # Regex to check valid passport number
    pattern = r'^[A-Z][1-9]\d\s?\d{4}[1-9]$'
    
    # Return true if the passport number matches the regex
    return bool(re.match(pattern, s))

# Test Cases
print(is_valid_passport_no("A21 90457"))  
print(is_valid_passport_no("A0296457"))   
print(is_valid_passport_no("Q2096453"))   
print(is_valid_passport_no("12096457"))   
print(is_valid_passport_no("A209645704"))

using System;
using System.Text.RegularExpressions;

class Program
{
    // Function to validate the passport number
    static bool IsValidPassportNo(string str)
    {
        // Regex to check valid passport number
        string pattern = @"^[A-Z][1-9]\d\s?\d{4}[1-9]$";
        Regex regex = new Regex(pattern);

        // Return true if the passport number matches the regex
        return regex.IsMatch(str);
    }

    static void Main()
    {
        // Test Case 1:
        string str1 = "A21 90457"; // Valid format
        Console.WriteLine(IsValidPassportNo(str1)); 

        // Test Case 2:
        string str2 = "A0296457"; // Valid format (no space)
        Console.WriteLine(IsValidPassportNo(str2)); 

        // Test Case 3:
        string str3 = "Q2096453"; // Valid format
        Console.WriteLine(IsValidPassportNo(str3)); 

        // Test Case 4:
        string str4 = "12096457"; // Invalid (does not start with a letter)
        Console.WriteLine(IsValidPassportNo(str4)); 

        // Test Case 5:
        string str5 = "A209645704";
        Console.WriteLine(IsValidPassportNo(str5));
    }
}

function isValidPassportNo(str) {
    // Regex to check valid passport number
    const pattern = /^[A-Z][1-9]\d\s?\d{4}[1-9]$/;

    // Return true if the passport number matches the regex
    return pattern.test(str);
}

// Test Cases
console.log(isValidPassportNo("A21 90457")); 
console.log(isValidPassportNo("A0296457"));   
console.log(isValidPassportNo("Q2096453"));   
console.log(isValidPassportNo("12096457"));   
console.log(isValidPassportNo("A209645704")); 

true
false
true
false
false

Time Complexity: O(N) for each test case, where N is the length of the given string.
Auxiliary Space: O(1)  

prashant_srivastava

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Article Tags :

• Strings
• Pattern Searching
• DSA
• java-regular-expression
• CPP-regex
• regular-expression

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Practice Tags :

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