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Margarita Cronin
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Asked: 2022-06-23T08:38:55+00:00 In:

Way to print out the contents of a std::vector to the screen in c++.

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Hello experts, I’m new to programming, so my understanding is still poor. Please guide me a simple way to print out the contents of a std::vector to the screen in c++. I really appreciate your help. Thanks in advance.

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1 Answer

  1. Best Answer
    Expert

    Hi, I’m happy to be able to help you. Hope some of my methods below will be useful to print out the contents of a std::vector to the screen in c++.

    Solution 1: Utilizing Indices
    The simplest approach is to iterate through the vector’s elements using a basic for-loop and access them using the [] operator/at() function with the appropriate index.

    #include <iostream>
#include <vector>

void print(std::vector<int> const &input)
{
for (int i = 0; i < input.size(); i++) {
std::cout << input.at(i) << ' ';
}
}

int main()
{
std::vector<int> input = { 1, 2, 3, 4, 5 };
print(input);

return 0;
}

    Output:

    1 2 3 4 5

     

    Solution 2: Utilizing the std::copy method
    With the aid of the output iterator std::ostream_iterator, we can use std::copy to copy the contents of the vector to the output stream std::cout.

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

void print(std::vector<int> const &input)
{
std::copy(input.begin(),
input.end(),
std::ostream_iterator<int>(std::cout, " "));
}

int main()
{
std::vector<int> input = { 1, 2, 3, 4, 5 };
print(input);

return 0;
}

    Same output as above.

    Solution 3: Utilizing Range-based for-loop
    For printing elements of a container with C++11, the suggested method is to use a range-based for-loop:

    #include <iostream>
#include <vector>

void print(std::vector<int> const &input)
{
for (auto const &i: input) {
std::cout << i << " ";
}
}

int main()
{
std::vector<int> input = { 1, 2, 3, 4, 5 };
print(input);

return 0;
}

    Same output as above.

    Solution 4: Utilizing std::for each function.
    It applies a function to each element in a range that is defined by two input iterators. The function may take the form of a lambda expression, an item of one class overloading the () operator, or a unary function.

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

void print(const int &i) {
std::cout << i << ' ';
}

struct myclass
{
void operator() (int i) {
std::cout << i << ' ';
}
} ob;

void print_vector(std::vector<int> const &input)
{
// specify a lambda expression
std::for_each(input.begin(),
input.end(),
[](const auto &e) {
std::cout << e << " ";
});

// or pass an object of a class overloading the `()operator`
// std::for_each(input.begin(), input.end(), ob);

// or specify a function
// std::for_each(input.begin(), input.end(), print);
}

int main()
{
std::vector<int> input = { 1, 2, 3, 4, 5 };
print_vector(input);

return 0;
}

    The output is the same as above.

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