C++ isdigit() Query for converting a char array to an int array

Question

I am trying to convert an input character array, to an int array in c++. Inputs would be in a format like: 'M 911843 6', where the first value of the char array is a uppercase letter, which I convert to an ASCII value and -55.

Edit: I should also mention I just want to use the iostream library

The last value of the char array can be a letter or number also.

I want to retain the exact number value of any input in the char array, which is why I convert to an ASCII value and -48, which retains the same number, but stored as an int value:

I use the checkdigit() function to check if the char input is a number or not.

The difficulty I am facing is that the input will always have a blank space at i[1] and i[8] (if we count i[0] as the first value) - so I try to give them an int value of 0 (int of a " " is 0)

Upon several debugging attempts, I found that it is after the blank space is given a 0 value, the output in my for loop keeps outputting the wrong values, I suspect it has something to do with the isdigit() function in my for loop.

If the spaces from M 911843 6 were removed, the int output is usually fine, e.g. a char input of M9118436 will return an int array of [22][9][1][1][8][4][3][6].

The output with spaces: [22][0][-183][-120][37][-118][-59][72][0][-55]

Ideal output: [22][0][9][1][1][8][4][3][0][6]

The code is listed below, any help or advice would be greatly appreciated, thanks!!

#include <iostream>
using namespace std;
int main() {
    char a[10];
    int z[10];
    int i = 0;
    int r; //result of the isdigit check (0 or 1)

    cout << "in      ";
    cin >> a;


    for (int i = 0; i < 10; i++) {
        r = isdigit(a[i]);
        if (r == 0) {
            if (i==1 || i==8)
                z[i] = 0;
            else z[i] = int(a[i]) - 55;
        }
        else {
            z[i] = int(a[i]) - 48;
        }
    }

    cout << z[0] << "\n" << z[1] << "\n"<< z[2]<< "\n" << z[3] << "\n"<< z[4] << "\n"<< z[5] << "\n"<< z[6] << "\n"<< z[7]<< "\n" << z[8] << "\n"<< z[9];


    return 0;
}

Standard std::string for your strings, and std::transform to convert to a std::vector<int>? Can use e.g. std::copy_if to copy the string to itself to remove spaces. — Some programmer dude
– Some programmer dude, Commented Feb 18, 2022 at 10:10

Serge Ballesta · Accepted Answer · 2022-02-18 10:23:53Z

0

The problem is that cin >> a; does not read sizeof(a) characters, but up to the first space character and will terminate that with a null.

That means that you array will containt 'M', '\0' and 8 uninitialized characters. You must read the characters one at a time with unformatted reads:

for (auto& c : a) {
    cin.get(c);
    if (!cin) {
        cerr << "Incorrect input\n";
        return EXIT_FAILURE;
    }
}

answered Feb 18, 2022 at 10:23

Serge Ballesta

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IsaOG · Accepted Answer · 2022-02-22 12:22:40Z

0

Just a follow on from Serge's answer which gave me a good understanding of how strings are read - I solved my problem using cin.getline() function.

answered Feb 22, 2022 at 12:22

IsaOG

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