Gap Buffer | Deletion Operation

We have discussed

Gap buffer

and insert operations. In this post,

delete operation

is discussed. When we want to delete a character these three cases may arise.

• Characters to be deleted is at cursor position: Let’s assume we want to delete “FOR” from “FORGEEKS”, since the cursor (gap_left) is at desired position the character is deleted i.e. the gap takes the character inside itself and the character gets deleted.
• Characters to be deleted is left of cursor position: For this case since “FOR” is left to the cursor position we must reach to the desired position by using left() as in previous article. Now, we can delete “FOR” as in case 1.
• Characters to be deleted is right of cursor position: For this case also the cursor position is right to the desired position we must reach there by using right() as in previous article. Now, we can delete “FOR” as in case 1.

Implementing Gap Buffer with Deletion

CPP

// C++ program of implementation
// of gap buffer with Deletion

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

char buffer[50];
int gap_size = 10;
int gap_left = 0;
int gap_right = gap_size - gap_left - 1;
int size = 10;

// Function that is used to grow the gap
// at index position and return the array

void grow(int k, int position)
{

    char a[size];

    // Copy characters of buffer to a[]
    // after position
    for (int i = position; i < size; i++) {
        a[i - position] = buffer[i];
    }

    // Insert a gap of k from index position
    // gap is being represented by '-'
    for (int i = 0; i < k; i++) {
        buffer[i + position] = '_';
    }

    // Reinsert the remaining array
    for (int i = 0; i < position + k; i++) {
        buffer[position + k + i] = a[i];
    }

    size += k;
    gap_right += k;
}

// Function that is used to move the gap
// left in the array
void left(int position)
{
    // Move the gap left character by character
    // and the buffers
    while (position < gap_left) {
        gap_left--;
        gap_right--;
        buffer[gap_right + 1] = buffer[gap_left];
        buffer[gap_left] = '_';
    }
}

// Function that is used to move the gap
// right in the array
void right(int position)
{
    // Move the gap right character by character
    // and the buffers
    while (position > gap_left) {
        gap_left++;
        gap_right++;
        buffer[gap_left - 1] = buffer[gap_right];
        buffer[gap_right] = '_';
    }
}

// Function to control the movement of gap
// by checking its position to the point of
// insertion
void move_cursor(int position)
{
    if (position < gap_left) {
        left(position);
    }
    else {
        right(position);
    }
}

// Function to insert the string to the buffer
// at point position
void insert(string input, int position)
{
    int len = input.length();
    int i = 0;

    // If the point is not the gap check
    // and move the cursor to that point
    if (position != gap_left) {
        move_cursor(position);
    }

    // Insert characters one by one
    while (i < len) {
        // If the gap is empty grow the size
        if (gap_right == gap_left) {
            int k = 10;
            grow(k, position);
        }

        // Insert the character in the gap and
        // move the gap
        buffer[gap_left] = input[i];
        gap_left++;
        i++;
        position++;
    }
}

// Function to delete the character buffer
// at point position
void deleetion(int position)
{
    // If the point is not the gap check
    // and move the cursor to that point
    if (position + 1 != gap_left) {
        move_cursor(position + 1);
    }

    // Reduce the gap_left
    gap_left -= 1;
    buffer[gap_left] = '_';
}

// Driver code
int main()
{
    // Initializing the gap buffer with size 10
    for (int i = 0; i < 10; i++) {
        buffer[i] = '_';
    }

    cout << "Initializing the gap buffer "
        << "with size 10" << endl;

    for (int i = 0; i < size; i++) {
        cout << buffer[i] << " ";
    }

    cout << endl;

    // Inserting a string to buffer
    string input = "GEEKSGEEKS";
    int position = 0;

    insert(input, position);

    cout << endl;
    cout << "Inserting a string to buffer"
        << ": GEEKSGEEKS" << endl;
    cout << "Output: ";
    for (int i = 0; i < size; i++) {
        cout << buffer[i] << " ";
    }

    input = "FOR";
    position = 5;

    // Inserting a string to buffer
    insert(input, position);

    cout << endl;
    cout << endl;

    cout << "Inserting a string to buffer"
        << ": FOR" << endl;
    cout << "Output: ";
    for (int i = 0; i < size; i++) {
        cout << buffer[i] << " ";
    }

    position = 5;

    // Deletion a character from buffer
    deleetion(position);

    cout << endl;
    cout << endl;

    cout << "Deleting character at position 5"
        << endl;
    cout << "Output: ";
    for (int i = 0; i < size; i++) {
        cout << buffer[i] << " ";
    }

    position = 6;

    // Deletion a character from buffer
    deleetion(position);

    cout << endl;
    cout << endl;

    cout << "Deleting character at position 6"
        << endl;
    cout << "Output: ";
    for (int i = 0; i < size; i++) {
        cout << buffer[i] << " ";
    }

    position = 5;

    // Deletion a character from buffer
    deleetion(position);

    cout << endl;
    cout << endl;

    cout << "Deleting character at position 5"
        << endl;
    cout << "Output: ";
    for (int i = 0; i < size; i++) {
        cout << buffer[i] << " ";
    }

    input = "HELLO";
    position = 0;

    // Inserting a string to buffer
    insert(input, position);

    cout << endl;
    cout << endl;

    cout << "Inserting a string to buffer"
        << ": HELLO" << endl;
    cout << "Output: ";
    for (int i = 0; i < size; i++) {
        cout << buffer[i] << " ";
    }

    return 0;
}

Java

public class GapBuffer {
    // Define the buffer and gap variables
    private char[] buffer;
    private int gapSize = 10;
    private int gapLeft = 0;
    private int gapRight = gapSize - 1;
    private int size = 10;

    // Constructor to initialize the gap buffer
    public GapBuffer() {
        buffer = new char[50];
        for (int i = 0; i < 10; i++) {
            buffer[i] = '_';
        }
    }

    // Function to increase the size of the gap
    public void grow(int k, int position) {
        char[] a = new char[size];
        System.arraycopy(buffer, position, a, 0, size - position);
        for (int i = 0; i < k; i++) {
            buffer[i + position] = '_';
        }
        System.arraycopy(a, 0, buffer, position + k, size - position);
        size += k;
        gapRight += k;
    }

    // Function to move the gap to the left
    public void left(int position) {
        while (position < gapLeft) {
            gapLeft--;
            gapRight--;
            buffer[gapRight + 1] = buffer[gapLeft];
            buffer[gapLeft] = '_';
        }
    }

    // Function to move the gap to the right
    public void right(int position) {
        while (position > gapLeft) {
            gapLeft++;
            gapRight++;
            buffer[gapLeft - 1] = buffer[gapRight];
            buffer[gapRight] = '_';
        }
    }

    // Function to move the cursor to the desired position
    public void moveCursor(int position) {
        if (position < gapLeft) {
            left(position);
        } else {
            right(position);
        }
    }

    // Function to insert a string at a given position
    public void insert(String input, int position) {
        int len = input.length();
        int i = 0;
        if (position != gapLeft) {
            moveCursor(position);
        }
        while (i < len) {
            if (gapRight == gapLeft) {
                int k = 10;
                grow(k, position);
            }
            buffer[gapLeft] = input.charAt(i);
            gapLeft++;
            i++;
            position++;
        }
    }

    // Function to delete a character at a given position
    public void deletion(int position) {
        if (position + 1 != gapLeft) {
            moveCursor(position + 1);
        }
        gapLeft -= 1;
        buffer[gapLeft] = '_';
    }

    // Function to print the current state of the buffer
    public void printBuffer() {
        for (int i = 0; i < size; i++) {
            System.out.print(buffer[i] + " ");
        }
        System.out.println();
    }

    // Main function to demonstrate the gap buffer operations
    public static void main(String[] args) {
        GapBuffer gapBuffer = new GapBuffer();
        System.out.println("Initializing the gap buffer with size 10");
        gapBuffer.printBuffer();

        System.out.println("\nInserting a string to buffer: GEEKSGEEKS");
        gapBuffer.insert("GEEKSGEEKS", 0);
        gapBuffer.printBuffer();

        System.out.println("\nInserting a string to buffer: FOR");
        gapBuffer.insert("FOR", 5);
        gapBuffer.printBuffer();

        System.out.println("\nDeleting character at position 5");
        gapBuffer.deletion(5);
        gapBuffer.printBuffer();

        System.out.println("\nDeleting character at position 6");
        gapBuffer.deletion(6);
        gapBuffer.printBuffer();

        System.out.println("\nDeleting character at position 5");
        gapBuffer.deletion(5);
        gapBuffer.printBuffer();

        System.out.println("\nInserting a string to buffer: HELLO");
        gapBuffer.insert("HELLO", 0);
        gapBuffer.printBuffer();
    }
}

Python3

class GapBuffer:
    def __init__(self):
        # Initializing the gap buffer
        self.buffer = ['_']*50
        self.gapSize = 10
        self.gapLeft = 0
        self.gapRight = self.gapSize - 1
        self.size = 10

    def grow(self, k, position):
        # Increasing the size of the gap
        a = self.buffer[position:self.size]
        self.buffer[position:position+k] = ['_']*k
        self.buffer[position+k:position+k+self.size-position] = a
        self.size += k
        self.gapRight += k

    def left(self, position):
        # Moving the gap to the left
        while position < self.gapLeft:
            self.gapLeft -= 1
            self.gapRight -= 1
            self.buffer[self.gapRight + 1] = self.buffer[self.gapLeft]
            self.buffer[self.gapLeft] = '_'

    def right(self, position):
        # Moving the gap to the right
        while position > self.gapLeft:
            self.gapLeft += 1
            self.gapRight += 1
            self.buffer[self.gapLeft - 1] = self.buffer[self.gapRight]
            self.buffer[self.gapRight] = '_'

    def moveCursor(self, position):
        # Moving the cursor to the desired position
        if position < self.gapLeft:
            self.left(position)
        else:
            self.right(position)

    def insert(self, input, position):
        # Inserting a string at a given position
        len_input = len(input)
        i = 0
        if position != self.gapLeft:
            self.moveCursor(position)
        while i < len_input:
            if self.gapRight == self.gapLeft:
                k = 10
                self.grow(k, position)
            self.buffer[self.gapLeft] = input[i]
            self.gapLeft += 1
            i += 1
            position += 1

    def deletion(self, position):
        # Deleting a character at a given position
        if position + 1 != self.gapLeft:
            self.moveCursor(position + 1)
        self.gapLeft -= 1
        self.buffer[self.gapLeft] = '_'

    def printBuffer(self):
        # Printing the current state of the buffer
        print(' '.join(self.buffer[:self.size]))

if __name__ == "__main__":
    gapBuffer = GapBuffer()
    print("Initializing the gap buffer with size 10")
    gapBuffer.printBuffer()

    print("\nInserting a string to buffer: GEEKSGEEKS")
    gapBuffer.insert("GEEKSGEEKS", 0)
    gapBuffer.printBuffer()

    print("\nInserting a string to buffer: FOR")
    gapBuffer.insert("FOR", 5)
    gapBuffer.printBuffer()

    print("\nDeleting character at position 5")
    gapBuffer.deletion(5)
    gapBuffer.printBuffer()

    print("\nDeleting character at position 6")
    gapBuffer.deletion(6)
    gapBuffer.printBuffer()

    print("\nDeleting character at position 5")
    gapBuffer.deletion(5)
    gapBuffer.printBuffer()

    print("\nInserting a string to buffer: HELLO")
    gapBuffer.insert("HELLO", 0)
    gapBuffer.printBuffer()

C#

using System;
using System.Linq;

public class GapBuffer
{
    private char[] buffer;
    private int gapSize;
    private int gapLeft;
    private int gapRight;
    private int size;

    public GapBuffer()
    {
        // Initializing the gap buffer
        this.buffer = Enumerable.Repeat('_', 50).ToArray();
        this.gapSize = 10;
        this.gapLeft = 0;
        this.gapRight = this.gapSize - 1;
        this.size = 10;
    }

    private void Grow(int k, int position)
    {
        // Increasing the size of the gap
        var a = this.buffer.Skip(position).Take(this.size - position).ToArray();
        Array.Copy(a, 0, this.buffer, position + k, this.size - position);
        Array.Fill(this.buffer, '_', position, k);
        this.size += k;
        this.gapRight += k;
    }

    private void Left(int position)
    {
        // Moving the gap to the left
        while (position < this.gapLeft)
        {
            this.gapLeft--;
            this.gapRight--;
            this.buffer[this.gapRight + 1] = this.buffer[this.gapLeft];
            this.buffer[this.gapLeft] = '_';
        }
    }

    private void Right(int position)
    {
        // Moving the gap to the right
        while (position > this.gapLeft)
        {
            this.gapLeft++;
            this.gapRight++;
            this.buffer[this.gapLeft - 1] = this.buffer[this.gapRight];
            this.buffer[this.gapRight] = '_';
        }
    }

    public void MoveCursor(int position)
    {
        // Moving the cursor to the desired position
        if (position < this.gapLeft)
        {
            this.Left(position);
        }
        else
        {
            this.Right(position);
        }
    }

    public void Insert(string input, int position)
    {
        // Inserting a string at a given position
        int len_input = input.Length;
        int i = 0;
        if (position != this.gapLeft)
        {
            this.MoveCursor(position);
        }
        while (i < len_input)
        {
            if (this.gapRight == this.gapLeft)
            {
                int k = 10;
                this.Grow(k, position);
            }
            this.buffer[this.gapLeft] = input[i];
            this.gapLeft++;
            i++;
            position++;
        }
    }

    public void Deletion(int position)
    {
        // Deleting a character at a given position
        if (position + 1 != this.gapLeft)
        {
            this.MoveCursor(position + 1);
        }
        this.gapLeft--;
        this.buffer[this.gapLeft] = '_';
    }

    public void PrintBuffer()
    {
        // Printing the current state of the buffer
        Console.WriteLine(new string(this.buffer.Take(this.size).ToArray()));
    }
}

class Program
{
    static void Main(string[] args)
    {
        var gapBuffer = new GapBuffer();
        Console.WriteLine("Initializing the gap buffer with size 10");
        gapBuffer.PrintBuffer();

        Console.WriteLine("\nInserting a string to buffer: GEEKSGEEKS");
        gapBuffer.Insert("GEEKSGEEKS", 0);
        gapBuffer.PrintBuffer();

        Console.WriteLine("\nInserting a string to buffer: FOR");
        gapBuffer.Insert("FOR", 5);
        gapBuffer.PrintBuffer();

        Console.WriteLine("\nDeleting character at position 5");
        gapBuffer.Deletion(5);
        gapBuffer.PrintBuffer();

        Console.WriteLine("\nDeleting character at position 6");
        gapBuffer.Deletion(6);
        gapBuffer.PrintBuffer();

        Console.WriteLine("\nDeleting character at position 5");
        gapBuffer.Deletion(5);
        gapBuffer.PrintBuffer();

        Console.WriteLine("\nInserting a string to buffer: HELLO");
        gapBuffer.Insert("HELLO", 0);
        gapBuffer.PrintBuffer();
    }
}

Javascript

class GapBuffer {
    constructor() {
        // Initializing the gap buffer
        this.buffer = Array(50).fill('_');
        this.gapSize = 10;
        this.gapLeft = 0;
        this.gapRight = this.gapSize - 1;
        this.size = 10;
    }

    grow(k, position) {
        // Increasing the size of the gap
        let a = this.buffer.slice(position, this.size);
        this.buffer.splice(position, this.size - position, ...Array(k).fill('_'));
        this.buffer.splice(position + k, a.length, ...a);
        this.size += k;
        this.gapRight += k;
    }

    left(position) {
        // Moving the gap to the left
        while (position < this.gapLeft) {
            this.gapLeft--;
            this.gapRight--;
            this.buffer[this.gapRight + 1] = this.buffer[this.gapLeft];
            this.buffer[this.gapLeft] = '_';
        }
    }

    right(position) {
        // Moving the gap to the right
        while (position > this.gapLeft) {
            this.gapLeft++;
            this.gapRight++;
            this.buffer[this.gapLeft - 1] = this.buffer[this.gapRight];
            this.buffer[this.gapRight] = '_';
        }
    }

    moveCursor(position) {
        // Moving the cursor to the desired position
        if (position < this.gapLeft) {
            this.left(position);
        } else {
            this.right(position);
        }
    }

    insert(input, position) {
        // Inserting a string at a given position
        let len_input = input.length;
        let i = 0;
        if (position != this.gapLeft) {
            this.moveCursor(position);
        }
        while (i < len_input) {
            if (this.gapRight == this.gapLeft) {
                let k = 10;
                this.grow(k, position);
            }
            this.buffer[this.gapLeft] = input[i];
            this.gapLeft++;
            i++;
            position++;
        }
    }

    deletion(position) {
        // Deleting a character at a given position
        if (position + 1 != this.gapLeft) {
            this.moveCursor(position + 1);
        }
        this.gapLeft--;
        this.buffer[this.gapLeft] = '_';
    }

    printBuffer() {
        // Printing the current state of the buffer
        console.log(this.buffer.slice(0, this.size).join(' '));
    }
}

// Main function to demonstrate the gap buffer operations
let gapBuffer = new GapBuffer();
console.log("Initializing the gap buffer with size 10");
gapBuffer.printBuffer();

console.log("\nInserting a string to buffer: GEEKSGEEKS");
gapBuffer.insert("GEEKSGEEKS", 0);
gapBuffer.printBuffer();

console.log("\nInserting a string to buffer: FOR");
gapBuffer.insert("FOR", 5);
gapBuffer.printBuffer();

console.log("\nDeleting character at position 5");
gapBuffer.deletion(5);
gapBuffer.printBuffer();

console.log("\nDeleting character at position 6");
gapBuffer.deletion(6);
gapBuffer.printBuffer();

console.log("\nDeleting character at position 5");
gapBuffer.deletion(5);
gapBuffer.printBuffer();

console.log("\nInserting a string to buffer: HELLO");
gapBuffer.insert("HELLO", 0);
gapBuffer.printBuffer();

Output

Initializing the gap buffer with size 10
_ _ _ _ _ _ _ _ _ _ 

Inserting a string to buffer: GEEKSGEEKS
Output: G E E K S G E E K S _ _ _ _ _ _ _ _ _ _ 

Inserting a string to buffer: FOR
Output: G E ...