How to user input the array elements in c++ in one

Question

I am new to c++ , Basically I belong to PHP . So I am trying to write a program just for practice, to sort an array . I have successfully created the program with static array value that is

// sort algorithm example
#include <iostream>     // std::cout
#include <algorithm>    // std::sort
#include <vector>       // std::vector


bool myfunction (int i,int j) { return (i<j); }

struct myclass { bool operator() (int i,int j) { return (i<j);} } myobject;

int main () {
   int myints[] = {55,82,12,450,69,80,93,33};
  std::vector<int> myvector (myints, myints+8);               

  // using default comparison (operator <):
  std::sort (myvector.begin(), myvector.begin()+4);           

  // using function as comp
  std::sort (myvector.begin()+4, myvector.end(), myfunction); 

  // using object as comp
  std::sort (myvector.begin(), myvector.end(), myobject);     

  // print out content:
  std::cout << "myvector contains:";
  for (std::vector<int>::iterator it=myvector.begin(); it!=myvector.end(); ++it)
    std::cout << ' ' << *it;
    std::cout << '\n';

  return 0;
}

its output is ok . But I want that the elements should input from user with space separated or , separated . So i have tried this

int main () {
    char values;
    std::cout << "Enter , seperated values :";
    std::cin >> values;
  int myints[] = {values};


  /* other function same */
}

it is not throwing an error while compiling. But op is not as required . It is

Enter , seperated values :20,56,67,45

myvector contains: 0 0 0 0 50 3276800 4196784 4196784

------------------ (program exited with code: 0) Press return to continue

Answer 1

You can use this simple example:

#include <iostream>
#include <string>
#include <sstream>
#include <algorithm>

using namespace std;

int main()
{
    stringstream ss;
    string str;
    getline(cin, str);
    replace( str.begin(), str.end(), ',', ' ');
    ss << str;

    int x = 0;
    while (ss >> x)
    {
        cout << x << endl;
    }
}

Live demo

---

or, if you want to have it more generic and nicely enclosed within a function returning std::vector:

#include <iostream>
#include <string>
#include <sstream>
#include <algorithm>
#include <vector>

using namespace std;

template <typename T>
vector<T> getSeparatedValuesFromUser(char separator = ',')
{
    stringstream ss;
    string str;
    getline(cin, str);
    replace(str.begin(), str.end(), separator, ' ');
    ss << str;

    T value{0};
    vector<T> values;
    while (ss >> value)
    {
        values.push_back(value);
    }

    return values;
}

int main()
{
    cout << "Enter , seperated values: ";
    auto values = getSeparatedValuesFromUser<int>();

    //display values
    cout << "Read values: " << endl;
    for (auto v : values)
    {
        cout << v << endl;
    }
}

Live demo

Answer 2

Let's see what you wrote:

int main () {
    char values;
    std::cout << "Enter , seperated values :";
    std::cin >> values; // read a single character
    int myints[] = {values}; // create a static array of size 1 containing the single character converted to an int

    /* other function same */
}

what you need is:

#include <sstream>
#include <string>

...

int main () {
    std::cout << "Enter space seperated values :";
    std::vector<int> myvector;
    std::string line;
    std::getline(std::cin, line); // read characters until end of line into the string
    std::istringstream iss(line); // creates an input string stream to parse the line
    while(iss >> value) // so long as values can be parsed
        myvector.push_back(value); // append the parsed value to the vector

    /* other function same */
}

If you want comma separated input you'll need to parse the comma as a single character in addition to the integer values.

Answer 3

Read in all the values into one string, then use a tokenizer to separate out the individual values.

How do I tokenize a string in C++?

Answer 4

What you are doing

int main () {
    char values; //Declare space for one character
    std::cout << "Enter , seperated values :"; //Ask user to enter a value
    std::cin >> values; //Read into values (one value only)
  int myints[] = {values}; // assign the first element to the ASCII code of whatever user typed.


  /* other function same */
}

In the language char works as an 8-bit integer. Through function overloading, different behavior can be implemented. Read about static polymorphism for more details how it works.

What you need to do

std::vector<int> values;
char ch_in;
std::string temp;
while(cin.get(ch_in)) {
    switch(ch_in) {
         case ',':
         case ' ': //Fall through
             values.push_back(atoi(temp.c_str()); //include cstdlib for atoi
             temp.clear();
             break;
         default:
             temp+=ch_in;
    }
}

You should put this in a separate function. With this skeleton, you can implement a more fancy syntax by adding more cases, but then you need something else than a std::vector<int> to put things into. You can (should?) also add error checking in the default case:

         default:
             if( (ch_in>='0' && ch_in<='9') 
                 || (temp.size()==0 && ch_in=='-') ) {
                 temp+=ch_in;
             }
             else {
                 cerr<<ch_in<<" is an illegal character here."
                 temp.clear();
             }

Answer 5

The above answers are very good for an arbitrary number of inputs, but if you allready know how many numbers will be put, you could do it like:

int[5] intList;
std::cin >> intList[0] >> intList[1] >> intList[2] >> intList[3] >> intList[4]

But please note that this method does not do any check if the numbers are put properly, so if there are for example letters or special characters in the input, you might get unexpected behavior.