How to Iterate Over a Vector of Pairs in C++?

In C++, vectors are dynamic arrays that allow users to store data in a contiguous memory location while pairs are data structures that allow the users to store two heterogeneous values together in the key-value pair. In this article, we are to learn how we can iterate over a vector of pairs in C++.

For Example,

Input:
myVector = <{1: "Geek"}, {2:" for"}, {3:" Geeks"} >
Output:
Vector Elements:
Key: 1,   Value: Geek
Key: 2,   Value: for
Key: 3,   Value: Geeks

Iterate Over a Vector of Pairs in C++

In C++, we can use the range-based for loop to iterate over each element of the vector of pairs. We can then access the first and second data members of each of the pair containers.

C++ Program to Iterator Over a Vector of Pairs

C++

// C++ Program to Iterate through a Vector of Pairs
#include <iostream>
#include <utility>
#include <vector>
using namespace std;

int main()
{
    // Declare a vector of pairs
    vector<pair<int, string> > vec;

    // Insert pairs inside the vector
    vec.push_back({ 1, "Geek" });
    vec.push_back({ 2, "for" });
    vec.push_back({ 3, "Geeks" });

    // Iterate through the vector of pairs using range-based
    // for loop
    cout << "Vector Elements:" << endl;
    for (auto pair : vec) {
        cout << "Key: " << pair.first
             << ", Value: " << pair.second << endl;
    }

    return 0;
}

Output

Vector Elements:
Key: 1, Value: Geek
Key: 2, Value: for
Key: 3, Value: Geeks

Time Complexity: O(N) where N is the number of elements present in the vector.
Auxilary Space : O(1)