How to change value of array using pointer?

Question

I am making a program which asks user for input and then separates it from comma and adds all separated values to an array. But as you can see, when I print the first value of the array, it doesnt print anything. Im a beginner.

#include <iostream>
#include <string>
#include "Header.h"
#include "Windows.h"
#include <array>
 
void Seperate(std::string input, std::string(*ptr)[50]) {

    if (input[input.length() - 1] == ',')
    {
        input.erase(input.length() - 1, 1);
    }

    std::string value;
    int length = input.length();
    for (int i = 0; i < length; i++) {
        if (input[i] != ',') {
            value += input[i];
        }
        else {
            (*ptr)[i] = value;
            value = "";
        }
    }

}
int main() {
    std::cout << "Enter comma seperated values to seperate: ";
    std::string input;
    std::cin >> input;
    std::string list[50];
    std::string(*ptr)[50] = &list;
    Seperate(input, ptr);
    std::cout << list[0];

}

This declaration std::string(*ptr)[50] = &list; does not make a sense. — Vlad from Moscow
– Vlad from Moscow, Commented Sep 15, 2021 at 7:50
You should have also a counter for word, (*ptr)[i] = value place the word at the ith place currently (where the comma is). — Jarod42
– Jarod42, Commented Sep 15, 2021 at 7:50
This is exactly what you want: stackoverflow.com/questions/14265581/… — Raffallo
– Raffallo, Commented Sep 15, 2021 at 7:56
std::vector<std::string> Seperate(std::string input, char sep = ', '); would be a better interface. — Jarod42
– Jarod42, Commented Sep 15, 2021 at 7:57
Are you aware that if you read into a string reading stops on first white-space occurring. So a, b, c would read in only a,. If you want to be able to cope with spaces you might be interested in std::getline — Aconcagua
– Aconcagua, Commented Sep 15, 2021 at 8:01

Prog_is_life · Accepted Answer · 2021-09-15 07:57:21Z

2

On this part you should use another int value to set your pointer values :

else {
        (*ptr)[i] = value;
        value = "";
    }

This should work for you like this :

std::string value;
int length = input.length();
int j = 0;
for (int i = 0; i < length; i++) {
    if (input[i] != ',') {
        value += input[i];
    }
    else {
        (*ptr)[j] = value;
        j = j + 1;
        value = "";
    }
}

answered Sep 15, 2021 at 7:57

Prog_is_life

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