How can I loop over pair in c++

Question

I am trying to print the elements in pair, but it's throwing an error: "no matching function call"
Code:

#include <utility>
#include <iostream>
using namespace std;

int main()
{
    pair<int, string> pairVec;
    pairVec = make_pair(1, "One");
    pairVec = make_pair(2, "Two");
    pairVec = make_pair(3, "Three");
    for(auto iter:pairVec)
    {
        std::cout << "First: " << iter.first << ", Second: "
                  << iter.second << std::endl;
    }
    return 0;
}

Solution

You're not making a vector at all. You probably wanted to do this instead:

int main()
{
    std::vector<pair<int, string>> pairVec;  // create a vector of pairs
    pairVec.emplace_back(1, "One"); // adding pairs to the vector
    pairVec.emplace_back(2, "Two");
    pairVec.emplace_back(3, "Three");
    for (auto iter : pairVec) {
        std::cout << "First: " << iter.first << ", Second: "
        << iter.second << std::endl;
    }
    return 0;
}

Comments

[CinCout]

You are overwriting pairVec. Hint: It is a single pair, not a vector of pairs.

[n. m.]

How many elements do you expect to see printed?

[molbdnilo]

What would the type of iter be? Try to fill in the type yourself, without writing auto.

[YSC]

What is the expected behavior of your code?

[Bobtheblobber]

Thanks for your time! Did I mention about the vector? I just need to iterate over the pair and print the elements

[n. m.]

@DheerajN Did I mention about the vector? Yes you very much did. Why did you #include <vector>? Why did you call your variable pairVec?

[Bobtheblobber]

@Blaze It is working fine! But when I mention the type of iterator instead of auto: std::vector<pair<int, string>>::const_iterator it, with regular for loop using it.begin....., it is throwing error "has no member named ‘first’"

[Blaze]

@DheerajN that's because the definition in that regular loop is different than what was auto-defined with the range based for loop (which is something rather unwieldy, in MSVC at least). But that works if you change ` iter.first` to iter->first and likewise for iter.second.

[von spotz]

The purpose of the std::pair here is to put order into the elements on the right hand side (std::pair.second). How would you change order, like swapping elements std::vector<std::pair<3, ...>> with std::vector<std::pair<8, ...>> ? Cheers