Vector of structs in C++

In this article, we will see how to initialize and use vector of structs in C++.

There are different ways to do it. This article will explain these methods clearly.
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Using Range Constructor

We can utilize the range constructor for the initialization of vector of structs in C++. It is useful when we need to make another copy of the existing vector. We will declare a different vector and copy the elements from the old vector using the range. We can access the elements of structs using ‘struct.element’ at the time of output.

Code:

#include 
#include 
#include 
using namespace std;

//Initializing Structure: Student
struct Student{
    string first_name;
    string last_name;
    int roll_no;
};

int main(){
    //creating vector of structure(Student)
    vector stu1 = {{"Steve", "Smith", 59},
                                {"Shane", "Watson", 57},
                                {"Adam", "Gilchrist", 3},
                                {"Ricky", "Ponting", 43}};
    //Passing the range of vector stu1 from first to last position
    //Creating another copy of vector stu1 
    vector new_stu(stu1.begin(), stu1.end());

    //Printing the new vector
    for (const auto &arr : new_stu) {
        cout << "First Name: " << arr.first_name << endl
             << "Last Name: " << arr.last_name << endl
             << "Roll Number: " << arr.roll_no << endl;
    }

    return 0;
}

Output

Using Initializer list

It is a simple method to create a vector of structs in C++. Here we initialize the container with the constant values. This method is better when it is important to have an initial state of some type for data structure.

Code:

#include 
#include 
#include 
using namespace std;

//Initializing Structure: Student
struct Student{
    string first_name;
    string last_name;
    int roll_no;
};

int main(){
    //creating vector of structure(Student)
    vector stu1 = {{"Steve", "Smith", 59},
                                {"Shane", "Watson", 57},
                                {"Adam", "Gilchrist", 3},
                                {"Ricky", "Ponting", 43}};

    //Printing the vector
    for (const auto &arr : stu1) {
        cout << "First Name: " << arr.first_name << endl
             << "Last Name: " << arr.last_name << endl
             << "Roll Number: " << arr.roll_no << endl;
    }

    return 0;
}

Output

Using custom constructor

In this method, we create a vector specific constructor which will initialize the vector with a given number filled with different values. Here we will take input from the user and we create a custom vector of structs with different values.
Code:

#include 
#include 
#include 
using namespace std;
struct Student{
    string first_name;
    string last_name;
    int age;
};

constexpr int count1 = 2;

int main(){
    //Custom Constructor to print the same values number of times
    vector stu1(count1, {"Donald", "Bradman", 32});

    //Custom constructor to take complete input from the user
    vector stu2;
    Student p;
    int count;
    cout<<"Enter the number of values you want to add:";
    cin>>count;
    for(int i = 0; i < count; ++i)
    {
        cout << "Please enter the first name, last name and roll number of a student:" << endl;
        string first_name, last_name;
        int age1;
        cin >> first_name;
        cin >> last_name;
        cin >> age1;
        p.first_name=first_name;
        p.last_name=last_name;
        p.age=age1;

        stu2.push_back(p);//Adding elements in the vector
    }
    //Printing the vector stu1
    cout<<"\nFirst Vector\n";
    for (const auto &arr1 : stu1) {
        cout << "First Name: " << arr1.first_name << endl
             << "Last Name: " << arr1.last_name << endl
             << "Age: " << arr1.age << endl;
    }
    //Printing the vector stu2
    cout<<"\nSecond Vector:\n";
    for (const auto &arr1 : stu2) {
        cout << "First Name: " << arr1.first_name << endl
             << "Last Name: " << arr1.last_name << endl
             << "Age: " << arr1.age << endl;
    }
    return 0;
}

Input

Output

Bonus Program

Program to sort a vector of structs in C++ according to the roll numbers of the students.

Code

#include 
#include 
#include 
using namespace std;

//Intializing struct
struct Student {
    int roll_no;
    string student_name;
};

//Printing the vector
void Print(vector& vect1) {

    for (int i = 0; i < vect1.size(); ++i) {
        cout << vect1[i].roll_no << ' ' << vect1[i].student_name << endl;
    }
    cout << endl;

}

int main() {
    //Filling values in the vector of student(struct) type
    vector vect;
    vect.push_back({ 72, "Louis" });
    vect.push_back({ 78, "Mike" });
    vect.push_back({ 26, "Harvey" });
    vect.push_back({ 15, "David" });

    cout << "Original Vector Before Sorting:\n" << endl;
    Print(vect);

    //Sorting ascendigly according to the roll number
    sort(vect.begin(), vect.end(), [](Student a, Student b) {
        return a.roll_no < b.roll_no;
    });

    cout << "Vector After Sorting:\n" << endl;
    Print(vect);
    return 0;
}

Output

Conclusion

In this article we demonstrated different methods that can create a vector of structs in C++. Custom Constructor method can be used in other ways as well as per the needs of the program.
Happy Learning!!