Multiple inputs in one line in C++

Question

I've newly started learning C++ and am stuck with this problem. I need to insert a (user inputted) number of elements in a single line with space separation. If the number of elements was known, I could just write cin >> var1 >> var2 >> ... >> varN;. But how do I do it with any number of elements (loop maybe)?

This is what I'm trying to do:

#include<bits/stdc++.h>
using namespace std;

int main() {
    int n;
    cin >> n;
    int arr[n];
    for (int i=0; i<n; i++) {
        //stuck here
    }
}

I could have written cin >> arr[i]; and proceeded, but that would require the user to press enter after every input, which I cannot do due to the question's restrictions. How do I write the code so that all my input for array elements can be given in a single line?

PS: I've seen several similar questions already answered on the site, but most of them involve implementations using vectors or are beyond my current level of understanding. A simpler solution will be appreciated.

So, you want each `arr[i]` to be read RIGHT AFTER the user type the space after? That is a bit strange. Does it make a difference in the final goal you want to achieve? Can you elaborate what are you doing on top of this (if possible)? — hackinghorn, Nov 30 '22 at 08:59
Elements are space separated, so they will all be read after pressing Enter — hackinghorn, Nov 30 '22 at 09:01
there is no language called C/C++. If you want to learn C++ you should read this [Why should I not `#include `?](https://stackoverflow.com/questions/31816095/why-should-i-not-include-bits-stdc-h) and maybe this [Why is “using namespace std;” considered bad practice?](https://stackoverflow.com/questions/1452721/why-is-using-namespace-std-considered-bad-practice). And note that C and C++ are two different languages. — 463035818_is_not_an_ai, Nov 30 '22 at 09:06
*'but that would require the user to press enter after every input'* That's completely incorrect, where did you get that idea? — john, Nov 30 '22 at 09:07
VLAs are not part of the C++ standard and therefore should not be used. You're incorrect about the behaviour you described though, see https://godbolt.org/z/WqbfrnrMd — fabian, Nov 30 '22 at 09:09
indeed, forgot this one [Why aren't variable-length arrays part of the C++ standard?](https://stackoverflow.com/questions/1887097/why-arent-variable-length-arrays-part-of-the-c-standard) — 463035818_is_not_an_ai, Nov 30 '22 at 09:13

score 4 · Accepted Answer · answered Nov 30 '22 at 09:00

4

cin>>arr[i] does not require the user to press enter after every input. You just need to give whitespace between the integer inputs. It will scan the array normally.

answered Nov 30 '22 at 09:00

Devansh_Jain_21

108
4

1

This is correct! Just put `cin >> arr[i];` in and test – hackinghorn Nov 30 '22 at 09:02
Ah, yes it works perfectly! I thought `cin` has newline as default separator for each input and thought there exists some alternative to change it to a whitespace. – RiverX15 Nov 30 '22 at 09:07
`cin` is a stream, there's no concept of a separator. It's the input operators and functions which might (or might not) define separators. – john Nov 30 '22 at 09:08

score 0 · Answer 2 · answered Nov 30 '22 at 10:07

You would probably want to replace your array with a std::vector to make it resizable in run time. If you do like in your example the program will not compile because n is not known when the program is built.

Here is a simple example

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

using namespace std;

int main() {
    int n = 0;
    cin >> n;
    vector<string> arr; // A vector (ie kind of a variable sized array)
    for (int i=0; i<n; i++) {
        string str;
        cin >> str; // Read a word
        arr.push_back(str); // Add a string to the vector
    }

    // To use the data
    for (int i = 0; i < arr.size(); ++i) {
        cout << arr.at(i) << "\n"; // Print value of vector
    }
    // or like this
    for (auto str: arr) {
        cout << str << "\n";
    }
}

Multiple inputs in one line in C++

2 Answers2