List of Vectors in C++ STL

In C++, the list of vector refers to the list container in which each element is a vector. In this article, we will learn about the list of vectors in C++.

Let’s take a look at an example:

#include <bits/stdc++.h>
using namespace std;

int main() {
    list<vector<int>> l = {{1, 3}, {2, 8}};
  
    for (auto v : l) {
        for (auto i : v)
            cout << i << " ";
        cout << endl;
    }
    return 0;
}

1 3 
2 8 

This article covers the syntax, basic operations, usage, and common queries of list of vectors in C++:

Syntax of List of Vector

The list of vectors can be defined by passing the vector of given type as template parameter

list<vector<T>> l;

where l is the name of list and T is the datatype of vector which we have to store in list.

Declaration and Initialization

Declaration and initialization are the process of creating a list of vectors and assigning it some initial value. In C++, it can be done in multiple ways as shown below:

1. Default Initialization

An empty list of vectors can be created using the below declaration. This can be filled later on in the program.

list<vector<T>> v;

2. Initialization with Size and Default Value

A list in with given number of vectors each of given size can be initialized to a default value using the below syntax. If a specific size can also be declared and initialized to the given value as default value.

list<vector<T>> v(size, val);

3. Initialization Using Initializer List

List of vectors can also be initialized using initializer list in a similar way as 2d vector.

list<vector<T>> v(m, vector<T>(n, val) = {{ v1, v2, v3….},
{ v1, v2, v3….}};

Let's take a look at an example:

#include <bits/stdc++.h>
using namespace std;

int main() {

    // Creating the list of vector
    list<vector<char>> l;

    // Inserting vectors into list
    l.push_back(vector<char>({'s', 'm', 'a'}));
    l.push_back(vector<char>({'d', 'f', 'g'}));
    l.push_back(vector<char>({'t', 'q', 'm'}));

    // Printing list of vectors
    for (auto v : l) {
        for (auto i : v)
            cout << i << " ";
        cout << endl;
    }
    return 0;
}

s m a 
d f g 
t q m 

Basic Operations

The basic operations on list of vectors have to be done by keeping in mind that each element is a vector.

The below example demonstrates how to perform these basic operations on a list of vectors:

#include <bits/stdc++.h>
using namespace std;

// Function to Print list of vectors
void print(list<vector<int>> &l) {
    for (auto v : l) {
        for (auto i : v)
            cout << i << " ";
        cout << endl;
    }
    cout << endl;
}

int main() {

    // Creating the list of vector
    list<vector<int>> l;

    vector<int> v1 = {1, 3, 7};
    vector<int> v2 = {2, 5, 4};
    vector<int> v3 = {9, 6, 7};
    vector<int> v4 = {11, 10, 8};

    // Inserting vectors to back of list
    l.push_back(v1);
    l.push_back(v2);

    // Insert vector to front of list
    l.push_front(v3);

    // Insert vector at 1st index
    auto it = l.begin();
    it++;
    l.insert(it, v4);
  
    print(l);

    // Remove the first vector from list
    l.erase(l.begin());
  
    print(l);
    return 0;
}

9 6 7 
11 10 8 
1 3 7 
2 5 4 

11 10 8 
1 3 7 
2 5 4 

bhuwanesh

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Article Tags :

• C++
• cpp-vector
• cpp-list
• CPP-forward-list

Practice Tags :

• CPP