How to take input in a single line in C++?

help
1

I want to take the input of the size of the array and the elements of the array in the same line separated by spaces e.g. If the size is 5 and elements are 0,1,2,3,4.
Input form: 5 0 1 2 3 4

2

In this case, you can just largely ignore how the data is formatted: the only thing we care about is that the things we want to read are separated by whitespace:

#include <iostream>
#include <vector>

using namespace std;

int main()
{
    int arraySize;
    cin >> arraySize;

    vector<int> array(arraySize);
    for (auto& element : array)
    {
        cin >> element;
    }

    cout << "Array: (" << arraySize << " elements)" << endl;
    for (const auto& element : array)
    {
        cout << element << endl;
    }
}

This will give the same output irrespective of whether the elements are on the same line or not:

$ echo "5 1 3 4 5 6" | ./a.out 
Array: (5 elements)
1
3
4
5
6
$ echo "5
1 3 4 5 6" | ./a.out
Array: (5 elements)
1
3
4
5
6
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3 
int n; cin >> n;
for (i, 0, n) cin >> array[i];
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4

Take input a list/array in few lines:

int n; cin >> n;
vector<int> a(n);
for (int &x : a) cin >> x;
5

what if we didn’t know size of array just like python?

6

Do you mean, “what if the size of the array is not provided in the input?”, i.e. you just have a single line, containing only the elements in the array and not the size?

1 Like
7

oh yes :slight_smile: … (20 char hueeeerrrrr)

1 Like
8

I’d probably do something like:

#include <vector>
#include <sstream>

using namespace std;

int main()
{
    string line;
    getline(cin, line);
    istringstream lineStream(line);

    int value;
    vector<int> array;
    while (lineStream >> value)
    {
        array.push_back(value);
    }

    cout << "Array: (" << array.size() << " elements)" << endl;
    for (const auto& element : array)
    {
        cout << element << endl;
    }
}

$ echo "11 7 6 1 8" | ./a.out
Array: (5 elements)
11
7
6
1
8

Edit:

Or if you want to read multiple lines:

#include <iostream>
#include <vector>
#include <sstream>

using namespace std;

int main()
{
    string line;
    while (getline(cin, line))
    {
        istringstream lineStream(line);

        int value;
        vector<int> array;
        while (lineStream >> value)
        {
            array.push_back(value);
        }

        cout << "Array: (" << array.size() << " elements)" << endl;
        for (const auto& element : array)
        {
            cout << element << endl;
        }
    }
}

$ echo "11 7 6 1 8
22 98 7 6 5 5 7 2332 33 3
67 8383 73 736 3 33" | ./a.out
Array: (5 elements)
11
7
6
1
8
Array: (10 elements)
22
98
7
6
5
5
7
2332
33
3
Array: (6 elements)
67
8383
73
736
3
33
5 Likes