User Input Validation Using Character Array in C++

问题

I am creating a c++ program to validate book ID using function in c++. The program must return 1 if the input is valid and 0 if the input is invalid. INPUT Pattern: "123-AB-12345" This will be considered as a valid input. The valid input is: (a) Total characters must be 12 (b) First three characters must be integers from 1 to 9 each. (c) 4th and 7th characters must be hiphen "-". (d) Last 5 characters must be integers from 1 to 9 each.

I tried the following way but I am not getting the desired answer. Need help plz

#include<iostream>
using namespace std;
bool isValidBookId(char bookId[13]);
int main()
{
    char book[13];
    cin.getline(book,12);
    bool id = isValidBookId(book);
    cout<<id;
}
bool isValidBookId(char bookId[13])
{
    int i;
    bool check1,check2,check3,check4,check5,check6;
    check1=check2=check3=check4=check5=true;
    if(bookId[12]=='\0'){
        check1=true;
    }       
    if(bookId[3]=='-')
    {
        check2=true;
    }
    if(bookId[6]=='-')
    {
        check3=true;
    }
    for(i=0; i<3;i++){
        if(bookId[i]>=0 || bookId[i]<=9)
        {
            check4=true;
        }
    }
    if(bookId[i]>= 'A' || bookId[i]<= 'Z')
    {
        check5=true;
    }
    for(i=7; i<12; i++)
    {
        if(bookId[i]>=0 || bookId[i]<=9)
        {
            check6=true;
        }
    }
    if(check1==true && check2==true && check3==true && check4==true && check5==true && check6==true)
    {
        return true;
    }
    else
    {
        return false;
    }
}

回答1:

There's a few errors that you have in your code.

First, you initialize all your checks to true, and never set anything to false, so the answer will always be true. Realistically, you want to initialize them all to false, and change to true when all the conditions are met, or assume true, and set to false when the condition is not met.

Second, your check for the values 0-9 is incorrect. You cannot compare bookId[i] to 0, you want to compare it to the character '0'. Also note that the question you have also says 1-9 not 0-9

Third, your check for A-Z is incorrect (note, this issue also applies to 0-9). You're code basically says is bookId[i] greater than or equal to 'A' OR less than or equal to Z, which is always going to be true.

I've written your code below:

bool isValidBookId( char bookId[13] ) {

    if ( bookId[12] != '\0' )
        return false;
    if ( bookId[3] != '-' )
        return false;
    if ( bookId[6] != '-' )
        return false;

    for ( int i = 0; i < 3; i++ ) {
        if ( bookId[i] < '1' || bookId[i] > '9' ) {
            return false;
        }
    }
    for ( int i = 4; i < 6; i++ ) {
        if ( bookId[i] < 'A' || bookId[i] > 'Z' ) {
            return false;
        }
    }
    for ( int i = 7; i < 12; i++ ) {
        if ( bookId[i] < '1' || bookId[i] > '9' ) {
            return false;
        }
    }

    return true;
}

This method doesn't require any Boolean variables. Instead, I assume true (the last return statement) and instead try to prove false. As soon as something is false, you can return without doing any other checks.

回答2:

Since the given code is in C-Style format, I would like to present 2 additional solutions in C++. I think the task is anyway to think about patterns and how these could be detected.

In my first solutions I just added more C++ elements. The 2nd solution should be the correct on.

Please see:

#include <iostream>
#include <regex>
#include <string>
#include <cctype>
#include <vector>

bool isValidBookId1(const std::string& bookId) {

    // Lambda to detect hyphen
    auto ishyphen = [](int i){ return static_cast<int>(i == '-');};

    // First check size of given string
    bool result{(bookId.size() == 12)};

    // Define the position of the types
    std::vector<size_t> digitIndex{0,1,2,7,8,9,10,11};
    std::vector<size_t> letterIndex{4,5};
    std::vector<size_t> hyphenIndex{3,6};

    // Check types
    if (result) for (size_t index : digitIndex) result = result && std::isdigit(bookId[index]);
    if (result) for (size_t index : letterIndex) result = result && std::isupper(bookId[index]);
    if (result) for (size_t index : hyphenIndex) result = result && ishyphen(bookId[index]);

    // Return resulting value
    return result;
}

bool isValidBookId2(const std::string& bookId) {

    // Define pattern as a regex
    std::regex re{R"(\d{3}-[A-Z]{2}-\d{5})"}; 

    // Check, if the book id matches the pattern
    return std::regex_match(bookId, re);
}

int main()
{
    // Get input from user
    if (std::string line{}; std::getline(std::cin, line)) {
        std::cout << "Check for valid Book input 1: " << isValidBookId1(line) << "\n";
        std::cout << "Check for valid Book input 2: " << isValidBookId2(line) << "\n";
    }
    return 0;
}

来源：https://stackoverflow.com/questions/59568183/user-input-validation-using-character-array-in-c

标签

c++

validation

user-input