I'm trying to ask the user to enter numbers that are put into a vector, then using a function call to count the numbers, why is this not working? I am only able to count the first number.
template <typename T>
void write_vector(const vector<T>& V)
{
cout << "The numbers in the vector are: " << endl;
for(int i=0; i < V.size(); i++)
cout << V[i] << " ";
}
int main()
{
int input;
vector<int> V;
cout << "Enter your numbers to be evaluated: " << endl;
cin >> input;
V.push_back(input);
write_vector(V);
return 0;
}
cin is delimited on space, so if you try to cin "1 2 3 4 5" into a single integer, your only going to be assigning 1 to the integer, a better option is to wrap your input and push_back in a loop, and have it test for a sentinel value, and on that sentinel value, call your write function. such as
int input;
cout << "Enter your numbers to be evaluated, and 10000 to quit: " << endl;
while(input != 10000) {
cin >> input;
V.push_back(input);
}
write_vector(V);
As is, you're only reading in a single integer and pushing it into your vector. Since you probably want to store several integers, you need a loop. E.g., replace
cin >> input;
V.push_back(input);
with
while (cin >> input)
V.push_back(input);
What this does is continually pull in ints from cin for as long as there is input to grab; the loop continues until cin finds EOF or tries to input a non-integer value. The alternative is to use a sentinel value, though this prevents you from actually inputting that value. Ex:
while ((cin >> input) && input != 9999)
V.push_back(input);
will read until you try to input 9999 (or any of the other states that render cin invalid), at which point the loop will terminate.
Other answers would have you disallow a particular number, or tell the user to enter something non-numeric in order to terminate input. Perhaps a better solution is to use std::getline() to read a line of input, then use std::istringstream to read all of the numbers from that line into the vector.
#include <iostream>
#include <sstream>
#include <vector>
int main(int argc, char** argv) {
std::string line;
int number;
std::vector<int> numbers;
std::cout << "Enter numbers separated by spaces: ";
std::getline(std::cin, line);
std::istringstream stream(line);
while (stream >> number)
numbers.push_back(number);
write_vector(numbers);
}
Also, your write_vector() implementation can be replaced with a more idiomatic call to the std::copy() algorithm to copy the elements to an std::ostream_iterator to std::cout:
#include <algorithm>
#include <iterator>
template<class T>
void write_vector(const std::vector<T>& vector) {
std::cout << "Numbers you entered: ";
std::copy(vector.begin(), vector.end(),
std::ostream_iterator<T>(std::cout, " "));
std::cout << '\n';
}
You can also use std::copy() and a couple of handy iterators to get the values into the vector without an explicit loop:
std::copy(std::istream_iterator<int>(stream),
std::istream_iterator<int>(),
std::back_inserter(numbers));
But that’s probably overkill.
You need a second integer.
int i,n;
vector<int> V;
cout << "Enter the amount of numbers you want to evaluate: ";
cin >> i;
cout << "Enter your numbers to be evaluated: " << endl;
while (V.size() < i && cin >> n){
V.push_back(n);
}
write_vector(V);
return 0;
You can simply do this with the help of for loop
->Ask on runtime from a user (how many inputs he want to enter) and the treat same like arrays.
int main() {
int sizz,input;
std::vector<int> vc1;
cout<< "How many Numbers you want to enter : ";
cin >> sizz;
cout << "Input Data : " << endl;
for (int i = 0; i < sizz; i++) {//for taking input form the user
cin >> input;
vc1.push_back(input);
}
cout << "print data of vector : " << endl;
for (int i = 0; i < sizz; i++) {
cout << vc1[i] << endl;
}
}
If you know the size use this
No temporary variable used just to store user input
int main()
{
cout << "Hello World!\n";
int n;//input size
cin >> n;
vector<int>a(n);
for (int i = 0; i < n; i++) {
cin >> a[i];
}
//to verify output user input printed below
for (auto x : a) {
cout << x << " ";
}
return 0;
}
One-liner to read a fixed amount of numbers into a vector (C++11):
#include <algorithm>
#include <iterator>
#include <iostream>
#include <vector>
#include <cstddef>
int main()
{
const std::size_t LIMIT{5};
std::vector<int> collection;
std::generate_n(std::back_inserter(collection), LIMIT,
[]()
{
return *(std::istream_iterator<int>(std::cin));
}
);
return 0;
}
Just add another variable.
int temp;
while (cin >> temp && V.size() < n){
V.push_back(temp);
}
You need a loop for that. So do this:
while (cin >> input) //enter any non-integer to end the loop!
{
V.push_back(input);
}
Or use this idiomatic version:
#include <iterator> //for std::istream_iterator
std::istream_iterator<int> begin(std::cin), end;
std::vector<int> v(begin, end);
write_vector(v);
You could also improve your write_vector as:
#include <algorithm> //for std::copy
template <typename T>
void write_vector(const vector<T>& v)
{
cout << "The numbers in the vector are: " << endl;
std::copy(v.begin(), v.end(), std::ostream_iterator<int>(std::cout, " "));
}
You probably want to read in more numbers, not only one. For this, you need a loop
int main()
{
int input = 0;
while(input != -1){
vector<int> V;
cout << "Enter your numbers to be evaluated: " << endl;
cin >> input;
V.push_back(input);
write_vector(V);
}
return 0;
}
Note, with this version, it is not possible to add the number -1 as it is the "end signal". Type numbers as long as you like, it will be aborted when you type -1.
would be easier if you specify the size of vector by taking an input :
int main()
{
int input,n;
vector<int> V;
cout<<"Enter the number of inputs: ";
cin>>n;
cout << "Enter your numbers to be evaluated: " << endl;
for(int i=0;i<n;i++){
cin >> input;
V.push_back(input);
}
write_vector(V);
return 0;
}
you have 2 options:
If you know the size of vector will be (in your case/example it's seems you know it):
vector<int> V(size)
for(int i =0;i<size;i++){
cin>>V[i];
}
if you don't and you can't get it in you'r program flow then:
int helper;
while(cin>>helper){
V.push_back(helper);
}
In this case your while loop will look like
int i = 0;
int a = 0;
while (i < n){
cin >> a;
V.push_back(a);
++i;
}
The initial size() of V will be 0, while int n contains any random value because you don't initialize it.
V.size() < n is probably false.
Silly me missed the "Enter the amount of numbers you want to evaluate: "
If you enter a n that's smaller than V.size() at that time, the loop will terminate.
I ran into a similar problem and this is how I did it. Using &modifying your code appropriately:
int main()
{
int input;
vector<int> V;
cout << "Enter your numbers to be evaluated: "
<< '\n' << "type "done" & keyboard Enter to stop entry"
<< '\n';
while ( (cin >> input) && input != "done") {
V.push_back(input);
}
write_vector(V);
return 0;
}
#include<bits/stdc++.h>
using namespace std;
int main()
{
int x,n;
cin>>x;
vector<int> v;
cout<<"Enter numbers:\n";
for(int i=0;i<x;i++)
{
cin>>n;
v.push_back(n);
}
//displaying vector contents
for(int p : v)
cout<<p<<" ";
}
A simple way to take input in vector.
If you know the size of the vector you can do it like this:
#include <bits/stdc++.h>
using namespace std;
int main() {
int n;
cin >> n;
vector<int> v(n);
for (auto &it : v) {
cin >> it;
}
}
These were two methods I tried. Both are fine to use.
int main() {
int size,temp;
cin>>size;
vector<int> ar(size);
//method 1
for(auto i=0;i<size;i++)
{ cin>>temp;
ar.insert(ar.begin()+i,temp);
}
for (auto i:ar)
cout <<i<<" ";
//method 2
for(int i=0;i<size;i++)
{
cin>>ar[i];
}
for (auto i:ar)
cout <<i<<" ";
return 0;
}
#include<iostream>
#include<vector>
#include<sstream>
using namespace std;
int main()
{
vector<string> v;
string line,t;
getline(cin,line);
istringstream iss(line);
while(iss>>t)
v.push_back(t);
vector<string>::iterator it;
for(it=v.begin();it!=v.end();it++)
cout<<*it<<endl;
return 0;
}
#include<iostream>
#include<vector>
#include<string>
using namespace std;
int main()
{
vector<string>V;
int num;
cin>>num;
string input;
while (cin>>input && num != 0) //enter any non-integer to end the loop!
{
//cin>>input;
V.push_back(input);
num--;
if(num==0)
{
vector<string>::iterator it;
for(it=V.begin();it!=V.end();it++)
cout<<*it<<endl;
};
}
return 0;
};
Source: Stackoverflow.com