Inputting string into multidimensional array

Question

I'm trying to make an array that hold multiple user input strings, I've tired structs and dynamic arrays and it does not work

I tried making a struct that holds a string, and tried making array of struct and it didn't work

#include <iostream>
#include <string>
#include <limits>



using namespace std;

int main()
{
    int rows;
    cin >> rows;
    string **arr = new string*[rows];
    for( int i = 0; i < rows; ++i)
    {
        arr[i]= new string[1];
    }
    for(int i = 0; i < rows; ++i)
    {
        getline(cin, arr[i][0]);
        cin.clear();
        cin.ignore(numeric_limits<streamsize>::max(), '\n');
    }


    for(int i = 0; i < rows; ++i)
    {
        cout << arr[i][0] << '\n';
    }


    for( int i = 0; i < rows; ++i)
    {
        delete [] arr[i];
    }
    delete [] arr;
return 0;
}

it allows rows + 1 inputs then crashes

The second level of indirection here is worthless. If you really want to use a dynamic sequence of std::string, you should use std::vector<std::string> as stated earlier. For this code, however, arr should be std::string *arr = new std::string[rows];, all referrals to arr[i][0] should be simply arr[i], and the last for loop should be completely thrown out. — WhozCraig
– WhozCraig, Commented Jul 30, 2019 at 7:08

nivpeled · Accepted Answer · 2019-07-30 07:33:35Z

4

Use std::vector and std:string types to easily get the job done:

#include <iostream>
#include <string>
#include <limits>
#include <vector>

using namespace std;

int main()
{
    int rows;
    cin >> rows;
    std::vector<std::string> vec;
    std::string s;

    // flush cin
    std::getline(std::cin, s);


    for (int i = 0; i < rows; ++i)
    {
        std::getline(std::cin, s);
        vec.push_back(s);
    }


    for (int i = 0; i < rows; ++i)
    {
        cout << vec[i] << '\n';
    }

    return 0;
}

edited Jul 30, 2019 at 7:33

answered Jul 30, 2019 at 7:07

nivpeled

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2 Comments

nivpeled Over a year ago

@WhozCraig correct, modified accordingly. Thank you!

nivpeled Over a year ago

@JackWilliam great, then you may mark my answer as best answer for this question.

Jarod42 · Accepted Answer · 2019-07-30 07:07:53Z

0

cin.clear();
cin.ignore(numeric_limits<streamsize>::max(), '\n');

should be done in case of error, not in regular cases.

Demo

edited Jul 30, 2019 at 7:07

answered Jul 30, 2019 at 7:03

Jarod42

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2 Comments

Ted Lyngmo Over a year ago

This doesn't answer OP:s question at all, does it?

Jarod42 Over a year ago

@TedLyngmo: I doesn't reproduce the "crash", but incorrect output, with provided fix, I got expected result (as shown in Demo). So even if OP style is bad, I don't see UB or similar.

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