Array of sets in C++

An array is defined as the collection of data items stored in a contiguous manner. An array stores different variables of the same type. It becomes easier to access the variables as they are stored at continuous locations.

For example

This is an array that contains six elements. Let’s say the array name is arr[]. Now, if we want to access the elements, they can access the indices 0 to n-1. Here, n is the size of the array.

Arr[0] = 10

Arr[1] = 20

Arr[2] = 30

Arr[3] = 40

Arr[4] = 50

Arr[5] = 60

Sets

A set is an associative container in which the elements are unique. Unlike an array, the value entered in a set cannot be modified after adding it. However, if we want to update the value in the set, we can remove it first and then enter the modified value.

Syntax

Example

set<int> s —– A set of integer values

set<char> c —- A set of character values

Array of sets

When we say an array of sets, it is a two-dimensional array with a fixed number of rows. Each row can have variable lengths.

In an array of sets, each array index stores a set. The set is accessible via iterators.

Array of sets in C++

Syntax

Example

set<int> s[3] —-> A array of set of int type with size 3

Insertion operation in the array of sets

Insertion will happen with the insert() function as each row is a set here. So, we insert using an array of sets using –

set_variable[row_number].insert(element)

Example

s[0].insert(10) —-> Inserts 10 in row 1

s[1].insert(20) —-> Inserts 20 in row 2

Code

  #include   using namespace std;  #define ROW 3  #define COL 4    int main()  {        set s[ROW]; // Create an array of sets        int num = 10; // Initial element to be inserted        for (int i = 0; i < ROW; i++) { // iterate in row          // Insert the column elements          for (int j = 0; j < COL; j++) {              s[i].insert(num);              num += 10;          }      }        // Display the array of sets      for (int i = 0; i < ROW; i++) {          cout << “Row ” << i + 1 << ” = ”               << “Elements at index ” << i << “: “;            // Print the array of sets          for (auto x : s[i])              cout << x << ” “;            cout << endl;      }        return 0;  }  

Output

Row 1 = Elements at index 0: 10 20 30 40   Row 2 = Elements at index 1: 50 60 70 80   Row 3 = Elements at index 2: 90 100 110 120

Deletion operation in an array of sets

When we say deletion of an element here, we are removing the element from the set. The function to remove an element from the set is erase().

Code

In this example, we have removed one element from set 3 and one element from set 2. Remember, the set index is i-1 as the array index starts at 0.

  #include   using namespace std;    // Fixing rows and column  #define ROW 3  #define COL 4    int main()  {      set s[ROW]; // Create array of set      int num = 10;        // Put elements in the set at a increment of 10      for (int i = 0; i < ROW; i++) {            // insert the column elements          for (int j = 0; j < COL; j++) {              s[i].insert(num);              num += 10;          }      }        cout << “Before removal elements are:”           << endl;        // Print elements after insertion      for (int i = 0; i < ROW; i++) {          cout << “Elements at index ”               << i << “: “;          for (auto x : s[i])              cout << x << ” “;          cout << endl;      }        s[2].erase(100); // Erase 100 from row 3 which means set 3        s[1].erase(50); // Erase 50 from row 2 which means set 2        cout << endl           << “After removal elements are:” << endl;        for (int i = 0; i < ROW; i++) {          cout << “Elements at index ” << i << “: “;            // Print the current set          for (auto x : s[i])              cout << x << ” “;            cout << endl;      }        return 0;  }  

Output

Before removal elements are:  Elements at index 0: 10 20 30 40   Elements at index 1: 50 60 70 80   Elements at index 2: 90 100 110 120     After removal elements are:  Elements at index 0: 10 20 30 40   Elements at index 1: 60 70 80   Elements at index 2: 90 110 120

Traversal operation in an array of sets

When we traverse an array of sets, we iterate through each set and print all the elements in that set. Iterators are used to traverse the set elements.

Code

In the below example, we create an array of sets having two rows. Row one has three elements in the set, and row 2 has two elements in the set.

To traverse an array of sets, we run an outer loop for the rows. In the inner loop, we use iterators to print each set.

  #include   using namespace std;  #define ROW 2 // Making a set of 2 rows  int main()  {        set s[ROW]; // create an array of sets with 2 rows        // Insertion in row 1      s[0].insert(10); // insertion in column 1      s[0].insert(15); // insertion in column 2      s[0].insert(35); // insertion in column 3        // Insertion in row 2      s[1].insert(20); // insertion in column 1      s[1].insert(30); // insertion in column 2        // Traversal in array of sets      for (int i = 0; i < ROW; i++) { // Iterate in the row          cout << “Elements at index ” << i << “: “;          // Now we have to Iterate in the set of a particular row          // So use an Iterate that runs from begin of set to end of that set          for (auto it = s[i].begin(); it != s[i].end(); it++) {                // Print the set value                cout << *it << ‘ ‘;          }            cout << endl;      }        return 0;  }  

Output

Elements at index 0: 10 15 35   Elements at index 1: 20 30

Next TopicSmart pointers in C++

Array of sets in C++

Array of sets in C++

Sets

Array of sets

Insertion operation in the array of sets

Deletion operation in an array of sets

Traversal operation in an array of sets

State variable analysis: Examples with explanation

C++ Deque

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