Question

How to mask a number with stars except the last 4 digits in C++

Answer 1

#include <iostream>
#include <string>

int main() {
    std::string cardNumber = "9003125334656789";
    
    std::string last4Digits = cardNumber.substr(cardNumber.length() - 4);
    
    std::string maskedNumber = std::string(cardNumber.length() - last4Digits.length(), '*') + last4Digits;
    
    std::cout << maskedNumber << std::endl;
}

 
 
/*
run:
 
************6789
 
*/

 

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Answer 2

#include <iostream>
#include <string>

std::string mask_number_with_stars_except_the_last_4_digits(std::string cardNumber) {
    std::string last4Digits = cardNumber.substr(cardNumber.length() - 4);
    
    std::string maskedNumber = std::string(cardNumber.length() - last4Digits.length(), '*') + last4Digits;
    
    return maskedNumber;
}

int main() {
    std::string cardNumber = "9003125334656789";
    
    std::string maskedNumber = mask_number_with_stars_except_the_last_4_digits(cardNumber);
    
    std::cout << maskedNumber << std::endl;
}

 
 
/*
run:
 
************6789
 
*/

 

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