writing integer input to vector container in C++

Question

likewise we do in array

for (.....)
  cin>>a[i];

how we can do this using vectors. i declared a vector of integers

vector<int> v;

now i need to take inputs from console and add append those in vector.i am using vector because i donot know the limit.

Answer 1

To insert integer to a vector from console and print everything out:

int input;
vector<int> v;
while(cin >> input){
 v.push_back(input);
}

for(int i = 0; i<v.size(); i++){
 cout<< v[i] <<endl;
}

And vector also provides you to print out the max size with:

cout << v.max_size()<<endl;

Answer 2

If the vector isn't initialized with an initial capacity, then use something like this:

int temp;
for (...) {
    cin >> temp;
    v.push_back(temp);
}

Answer 3

Slightly more compact versions:

#include <algorithm>
#include <iostream>
#include <iterator>
#include <vector>

std::istream_iterator< int > iterBegin( std::cin ), iterEnd;

// using the range constructor
std::vector< int > vctUserInput1( iterBegin, iterEnd );

// using the copy & back_inserter
std::vector< int > vctUserInput2;
std::copy( iterBegin, iterEnd, std::back_inserter( vctUserInput2 ) );

Answer 4

Try this

std::copy( std::istream_iterator<int>(std::cin),
            std::istream_iterator<int>(),
            std::back_inserter( v ) );

See here

You can simplify this to just creating the vector and initializing it with iterators:

std::vector<int>  v(std::istream_iterator<int>{std::cin},
                    std::istream_iterator<int>{});

Answer 5

The easiest solution is with an istream_iterator. You don't want std::copy, tough, because that's greedy. It will read everything. Instead, use this:

std::istream_iterator<int> iter(std::cin);
vector<int> v;
for(.....)
   v.push_back(*iter++);

Answer 6

Small program for taking input from user through vector in c++

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

int main()
{
    vector<int> v1;
    int input;
    cout<<"Enter elements in vector";
      for (int i=0;i<10;i++)
       {
         cin>>input;
         v1.push_back(input);
       }

       cout<<"Elements in vector";
       for (int i=0;i<10;i++)
        {
          cout<<v1[i]<<"\n";
        }
         return 0;
 }

Answer 7

When number of inputs are not given then we to code like that

#include<iostream>
using namespace std;

#include<vector>

int main()
{
    int i ;
    vector<int> v;
    while(i != -1)
    {
        cin >> i;
        v.push_back(i);
    }
}

/In above code i am taking input till user has not entered -1.In your question also there must be some condition given instead of number of inputs and if the number of inputs are given then it's very easy to take input.The code for that is:/

for (i=0; i<n; i++)
{
    cin >> i;
    v.push_back(i);
}

Answer 8

You can also dynamically allocate an array and then use it in a vector.

Here it is what you can do,

#include<bits/stdc++.h>
int main()
{
 int n;cin>>n;
 vector<int>v(n);
 for(int i=0;i<n;i++){
 cin>>v[i];
}
for(auto x:v){
cout<<x<<" "<<endl;
}
}

Its an Easy approach you can do.