Find the length of longest arithmetic progression

Here given code implementation process.

// C program
// Find the length of longest arithmetic progression
// In sorted data

#include <stdio.h>

//Display the elements of array
void print_data(int data[], int size)
{
	printf("\n Element :");
	for (int i = 0; i < size; ++i)
	{
		printf("  %d", data[i]);
	}
}
//returns the maximum of given two numbers
int max_num(int a, int b)
{
	if (a > b)
	{
		//When (a) is greater
		return a;
	}
	//When b is greater than or equal to a
	return b;
}
//returns the length of longest arithmetic progression  
void length_of_longest_ap(int data[], int size)
{
	//Display given element
	print_data(data, size);
	printf("\n Result  : ");
	if (size <= 2)
	{
		//When have two or less than 2 elements
		printf(" %d\n", size);
		return;
	}
	//Minimum 2 result are possible
	int result = 2;
	//Create storage to calculate result
	int auxiliary[size][size];
	//Loop controlling variables
	int i = 0;
	int j = 0;
	int k = 0;
	//Set initial value of created storage
	for (i = 0; i < size; i++)
	{
		// Set the [i] row and last column value is to 2
		auxiliary[i][size - 1] = 2;
	}
	// Get last-1 position of given data
	j = size - 2;
	while (j >= 1)
	{
		k = j + 1;
		i = j - 1;
		while (i >= 0 && k <= size - 1)
		{
			if (data[i] + data[k] < 2 * data[j])
			{
				k++;
			}
			else if (data[i] + data[k] > 2 * data[j])
			{
				auxiliary[i][j] = 2;
				i--;
			}
			else
			{
				auxiliary[i][j] = auxiliary[j][k] + 1;
				//Get result
				result = max_num(result, auxiliary[i][j]);
				k++;
				i--;
			}
		}
		while (i >= 0)
		{
			auxiliary[i][j] = 2;
			i--;
		}
		j--;
	}
	printf(" %d\n", result);
}
int main()
{
	//Define the collection of sorted integer values
	//This is test inputs
	int data1[] = {
		-3,
		0,
		3,
		7,
		9,
		12,
		14,
		15,
		19,
		21,
		27
	};
	int data2[] = {
		8,
		10,
		12,
		14,
		17
	};
	int data3[] = {
		5,
		8,
		10,
		12,
		14,
		16,
		15
	};
	int data4[] = {
		1,
		3,
		5,
		7,
		9,
		11,
		13
	};
	//Get the size of given data1
	int size = sizeof(data1) / sizeof(data1[0]);
	length_of_longest_ap(data1, size);
	//Get the size of given data2
	size = sizeof(data2) / sizeof(data2[0]);
	length_of_longest_ap(data2, size);
	//Get the size of given data3
	size = sizeof(data3) / sizeof(data3[0]);
	length_of_longest_ap(data3, size);
	//Get the size of given data4
	size = sizeof(data4) / sizeof(data4[0]);
	length_of_longest_ap(data4, size);
	return 0;
}

Output

 Element :  -3  0  3  7  9  12  14  15  19  21  27
 Result  :  6

 Element :  8  10  12  14  17
 Result  :  4

 Element :  5  8  10  12  14  16  15
 Result  :  5

 Element :  1  3  5  7  9  11  13
 Result  :  7
// Java program
// Find the length of longest arithmetic progression
// In sorted data
class ArithmeticProgression
{
	//Display the elements of array
	public void print_data(int[] data, int size)
	{
		System.out.print("\n Element :");
		for (int i = 0; i < size; ++i)
		{
			System.out.print("  " + data[i] );
		}
	}
	//returns the maximum of given two numbers
	public int max_num(int a, int b)
	{
		if (a > b)
		{
			//When (a) is greater
			return a;
		}
		//When b is greater than or equal to a
		return b;
	}
	//returns the length of longest arithmetic progression  
	public void length_of_longest_ap(int[] data, int size)
	{
		//Display given element
		print_data(data, size);
		System.out.print("\n Result : ");
		if (size <= 2)
		{
			//When have two or less than 2 elements
			System.out.print("  " + size + "\n");
			return;
		}
		//Minimum 2 result are possible
		int result = 2;
		//Create storage to calculate result
		int[][] auxiliary = new int[size][size];
		//Loop controlling variables
		int i = 0;
		int j = 0;
		int k = 0;
		//Set initial value of created storage
		for (i = 0; i < size; i++)
		{
			// Set the [i] row and last column value is to 2
			auxiliary[i][size - 1] = 2;
		}
		// Get last-1 position of given data
		j = size - 2;
		while (j >= 1)
		{
			k = j + 1;
			i = j - 1;
			while (i >= 0 && k <= size - 1)
			{
				if (data[i] + data[k] < 2 * data[j])
				{
					k++;
				}
				else if (data[i] + data[k] > 2 * data[j])
				{
					auxiliary[i][j] = 2;
					i--;
				}
				else
				{
					auxiliary[i][j] = auxiliary[j][k] + 1;
					//Get result
					result = max_num(result, auxiliary[i][j]);
					k++;
					i--;
				}
			}
			while (i >= 0)
			{
				auxiliary[i][j] = 2;
				i--;
			}
			j--;
		}
		System.out.print("  " + result + "\n");
	}
	public static void main(String[] args)
	{
		ArithmeticProgression obj = new ArithmeticProgression();
		//Define the collection of sorted integer values
		//This is test inputs
		int[] data1 = {
			-3,
			0,
			3,
			7,
			9,
			12,
			14,
			15,
			19,
			21,
			27
		};
		int[] data2 = {
			8,
			10,
			12,
			14,
			17
		};
		int[] data3 = {
			5,
			8,
			10,
			12,
			14,
			16,
			15
		};
		int[] data4 = {
			1,
			3,
			5,
			7,
			9,
			11,
			13
		};
		//Get the size of given data1
		int size = data1.length;
		obj.length_of_longest_ap(data1, size);
		//Get the size of given data2
		size = data2.length;
		obj.length_of_longest_ap(data2, size);
		//Get the size of given data3
		size = data3.length;
		obj.length_of_longest_ap(data3, size);
		//Get the size of given data4
		size = data4.length;
		obj.length_of_longest_ap(data4, size);
	}
}

Output

 Element :  -3  0  3  7  9  12  14  15  19  21  27
 Result :   6

 Element :  8  10  12  14  17
 Result :   4

 Element :  5  8  10  12  14  16  15
 Result :   5

 Element :  1  3  5  7  9  11  13
 Result :   7
//Include header file
#include <iostream>

using namespace std;
// C++ program
// Find the length of longest arithmetic progression
// In sorted data
class ArithmeticProgression
{
	public:
		//Display the elements of array
		void print_data(int data[], int size)
		{
			cout << "\n Element :";
			for (int i = 0; i < size; ++i)
			{
				cout << "  " << data[i];
			}
		}
	//returns the maximum of given two numbers
	int max_num(int a, int b)
	{
		if (a > b)
		{
			//When (a) is greater
			return a;
		}
		//When b is greater than or equal to a
		return b;
	}
	//returns the length of longest arithmetic progression  
	void length_of_longest_ap(int data[], int size)
	{
		//Display given element
		this->print_data(data, size);
		cout << "\n Result : ";
		if (size <= 2)
		{
			//When have two or less than 2 elements
			cout << "  " << size << "\n";
			return;
		}
		//Minimum 2 result are possible
		int result = 2;
		//Create storage to calculate result
		int auxiliary[size][size];
		//Loop controlling variables
		int i = 0;
		int j = 0;
		int k = 0;
		//Set initial value of created storage
		for (i = 0; i < size; i++)
		{
			// Set the [i] row and last column value is to 2
			auxiliary[i][size - 1] = 2;
		}
		// Get last-1 position of given data
		j = size - 2;
		while (j >= 1)
		{
			k = j + 1;
			i = j - 1;
			while (i >= 0 && k <= size - 1)
			{
				if (data[i] + data[k] < 2 * data[j])
				{
					k++;
				}
				else if (data[i] + data[k] > 2 * data[j])
				{
					auxiliary[i][j] = 2;
					i--;
				}
				else
				{
					auxiliary[i][j] = auxiliary[j][k] + 1;
					//Get result
					result = this->max_num(result, auxiliary[i][j]);
					k++;
					i--;
				}
			}
			while (i >= 0)
			{
				auxiliary[i][j] = 2;
				i--;
			}
			j--;
		}
		cout << "  " << result << "\n";
	}
};
int main()
{
	ArithmeticProgression obj = ArithmeticProgression();
	//Define the collection of sorted integer values
	//This is test inputs
	int data1[] = {
		-3 , 0 , 3 , 7 , 9 , 12 , 14 , 15 , 19 , 21 , 27
	};
	int data2[] = {
		8 , 10 , 12 , 14 , 17
	};
	int data3[] = {
		5 , 8 , 10 , 12 , 14 , 16 , 15
	};
	int data4[] = {
		1 , 3 , 5 , 7 , 9 , 11 , 13
	};
	//Get the size of given data1
	int size = sizeof(data1) / sizeof(data1[0]);
	obj.length_of_longest_ap(data1, size);
	//Get the size of given data2
	size = sizeof(data2) / sizeof(data2[0]);
	obj.length_of_longest_ap(data2, size);
	//Get the size of given data3
	size = sizeof(data3) / sizeof(data3[0]);
	obj.length_of_longest_ap(data3, size);
	//Get the size of given data4
	size = sizeof(data4) / sizeof(data4[0]);
	obj.length_of_longest_ap(data4, size);
	return 0;
}

Output

 Element :  -3  0  3  7  9  12  14  15  19  21  27
 Result :   6

 Element :  8  10  12  14  17
 Result :   4

 Element :  5  8  10  12  14  16  15
 Result :   5

 Element :  1  3  5  7  9  11  13
 Result :   7
//Include namespace system
using System;

// C# program
// Find the length of longest arithmetic progression
// In sorted data

class ArithmeticProgression
{
	//Display the elements of array
	public void print_data(int[] data, int size)
	{
		Console.Write("\n Element :");
		for (int i = 0; i < size; ++i)
		{
			Console.Write("  " + data[i]);
		}
	}
	//returns the maximum of given two numbers
	public int max_num(int a, int b)
	{
		if (a > b)
		{
			//When (a) is greater
			return a;
		}
		//When b is greater than or equal to a
		return b;
	}
	//returns the length of longest arithmetic progression  
	public void length_of_longest_ap(int[] data, int size)
	{
		//Display given element
		print_data(data, size);
		Console.Write("\n Result : ");
		if (size <= 2)
		{
			//When have two or less than 2 elements
			Console.Write("  " + size + "\n");
			return;
		}
		//Minimum 2 result are possible
		int result = 2;
		//Create storage to calculate result
		int[,] auxiliary = new int[size,size];
		//Loop controlling variables
		int i = 0;
		int j = 0;
		int k = 0;
		//Set initial value of created storage
		for (i = 0; i < size; i++)
		{
			// Set the [i] row and last column value is to 2
			auxiliary[i,size - 1] = 2;
		}
		// Get last-1 position of given data
		j = size - 2;
		while (j >= 1)
		{
			k = j + 1;
			i = j - 1;
			while (i >= 0 && k <= size - 1)
			{
				if (data[i] + data[k] < 2 * data[j])
				{
					k++;
				}
				else if (data[i] + data[k] > 2 * data[j])
				{
					auxiliary[i,j] = 2;
					i--;
				}
				else
				{
					auxiliary[i,j] = auxiliary[j,k] + 1;
					//Get result
					result = max_num(result, auxiliary[i,j]);
					k++;
					i--;
				}
			}
			while (i >= 0)
			{
				auxiliary[i,j] = 2;
				i--;
			}
			j--;
		}
		Console.Write("  " + result + "\n");
	}
	public static void Main(String[] args)
	{
		ArithmeticProgression obj = new ArithmeticProgression();
		//Define the collection of sorted integer values
		//This is test inputs
		int[] data1 = {
			-3 , 0 , 3 , 7 , 9 , 12 , 14 , 15 , 19 , 21 , 27
		};
		int[] data2 = {
			8 , 10 , 12 , 14 , 17
		};
		int[] data3 = {
			5 , 8 , 10 , 12 , 14 , 16 , 15
		};
		int[] data4 = {
			1 , 3 , 5 , 7 , 9 , 11 , 13
		};
		//Get the size of given data1
		int size = data1.Length;
		obj.length_of_longest_ap(data1, size);
		//Get the size of given data2
		size = data2.Length;
		obj.length_of_longest_ap(data2, size);
		//Get the size of given data3
		size = data3.Length;
		obj.length_of_longest_ap(data3, size);
		//Get the size of given data4
		size = data4.Length;
		obj.length_of_longest_ap(data4, size);
	}
}

Output

 Element :  -3  0  3  7  9  12  14  15  19  21  27
 Result :   6

 Element :  8  10  12  14  17
 Result :   4

 Element :  5  8  10  12  14  16  15
 Result :   5

 Element :  1  3  5  7  9  11  13
 Result :   7
<?php
// Php program
// Find the length of longest arithmetic progression
// In sorted data
class ArithmeticProgression
{
	//Display the elements of array
	public	function print_data( & $data, $size)
	{
		echo "\n Element :";
		for ($i = 0; $i < $size; ++$i)
		{
			echo "  ". $data[$i];
		}
	}
	//returns the maximum of given two numbers
	public	function max_num($a, $b)
	{
		if ($a > $b)
		{
			//When (a) is greater
			return $a;
		}
		//When b is greater than or equal to a
		return $b;
	}
	//returns the length of longest arithmetic progression  
	public	function length_of_longest_ap( & $data, $size)
	{
		//Display given element
		$this->print_data($data, $size);
		echo "\n Result : ";
		if ($size <= 2)
		{
			//When have two or less than 2 elements
			echo "  ". $size ."\n";
			return;
		}
		//Minimum 2 result are possible
		$result = 2;
		//Create storage to calculate result
		$auxiliary = array_fill(0, $size,  array_fill(0, $size, 0));
		//Loop controlling variables
		$i = 0;
		$j = 0;
		$k = 0;
		//Set initial value of created storage
		for ($i = 0; $i < $size; $i++)
		{
			// Set the [i] row and last column value is to 2
			$auxiliary[$i][$size - 1] = 2;
		}
		// Get last-1 position of given data
		$j = $size - 2;
		while ($j >= 1)
		{
			$k = $j + 1;
			$i = $j - 1;
			while ($i >= 0 && $k <= $size - 1)
			{
				if ($data[$i] + $data[$k] < 2 * $data[$j])
				{
					$k++;
				}
				else if ($data[$i] + $data[$k] > 2 * $data[$j])
				{
					$auxiliary[$i][$j] = 2;
					$i--;
				}
				else
				{
					$auxiliary[$i][$j] = $auxiliary[$j][$k] + 1;
					//Get result
					$result = $this->max_num($result, $auxiliary[$i][$j]);
					$k++;
					$i--;
				}
			}
			while ($i >= 0)
			{
				$auxiliary[$i][$j] = 2;
				$i--;
			}
			$j--;
		}
		echo "  ". $result ."\n";
	}
}

function main()
{
	$obj = new ArithmeticProgression();
	//Define the collection of sorted integer values
	//This is test inputs
	$data1 = array(-3, 0, 3, 7, 9, 12, 14, 15, 19, 21, 27);
	$data2 = array(8, 10, 12, 14, 17);
	$data3 = array(5, 8, 10, 12, 14, 16, 15);
	$data4 = array(1, 3, 5, 7, 9, 11, 13);
	//Get the size of given data1
	$size = count($data1);
	$obj->length_of_longest_ap($data1, $size);
	//Get the size of given data2
	$size = count($data2);
	$obj->length_of_longest_ap($data2, $size);
	//Get the size of given data3
	$size = count($data3);
	$obj->length_of_longest_ap($data3, $size);
	//Get the size of given data4
	$size = count($data4);
	$obj->length_of_longest_ap($data4, $size);
}
main();

Output

 Element :  -3  0  3  7  9  12  14  15  19  21  27
 Result :   6

 Element :  8  10  12  14  17
 Result :   4

 Element :  5  8  10  12  14  16  15
 Result :   5

 Element :  1  3  5  7  9  11  13
 Result :   7
// Node Js program
// Find the length of longest arithmetic progression
// In sorted data
class ArithmeticProgression
{
	//Display the elements of array
	print_data(data, size)
	{
		process.stdout.write("\n Element :");
		for (var i = 0; i < size; ++i)
		{
			process.stdout.write("  " + data[i]);
		}
	}
	//returns the maximum of given two numbers
	max_num(a, b)
	{
		if (a > b)
		{
			//When (a) is greater
			return a;
		}
		//When b is greater than or equal to a
		return b;
	}
	//returns the length of longest arithmetic progression  
	length_of_longest_ap(data, size)
	{
		//Display given element
		this.print_data(data, size);
		process.stdout.write("\n Result : ");
		if (size <= 2)
		{
			//When have two or less than 2 elements
			process.stdout.write("  " + size + "\n");
			return;
		}
		//Minimum 2 result are possible
		var result = 2;
		//Create storage to calculate result
		var auxiliary = Array(size).fill(0).map(() => new Array(size).fill(0));
		//Loop controlling variables
		var i = 0;
		var j = 0;
		var k = 0;
		//Set initial value of created storage
		for (i = 0; i < size; i++)
		{
			// Set the [i] row and last column value is to 2
			auxiliary[i][size - 1] = 2;
		}
		// Get last-1 position of given data
		j = size - 2;
		while (j >= 1)
		{
			k = j + 1;
			i = j - 1;
			while (i >= 0 && k <= size - 1)
			{
				if (data[i] + data[k] < 2 * data[j])
				{
					k++;
				}
				else if (data[i] + data[k] > 2 * data[j])
				{
					auxiliary[i][j] = 2;
					i--;
				}
				else
				{
					auxiliary[i][j] = auxiliary[j][k] + 1;
					//Get result
					result = this.max_num(result, auxiliary[i][j]);
					k++;
					i--;
				}
			}
			while (i >= 0)
			{
				auxiliary[i][j] = 2;
				i--;
			}
			j--;
		}
		process.stdout.write("  " + result + "\n");
	}
}

function main()
{
	var obj = new ArithmeticProgression();
	//Define the collection of sorted integer values
	//This is test inputs
	var data1 = [-3, 0, 3, 7, 9, 12, 14, 15, 19, 21, 27];
	var data2 = [8, 10, 12, 14, 17];
	var data3 = [5, 8, 10, 12, 14, 16, 15];
	var data4 = [1, 3, 5, 7, 9, 11, 13];
	//Get the size of given data1
	var size = data1.length;
	obj.length_of_longest_ap(data1, size);
	//Get the size of given data2
	size = data2.length;
	obj.length_of_longest_ap(data2, size);
	//Get the size of given data3
	size = data3.length;
	obj.length_of_longest_ap(data3, size);
	//Get the size of given data4
	size = data4.length;
	obj.length_of_longest_ap(data4, size);
}
main();

Output

 Element :  -3  0  3  7  9  12  14  15  19  21  27
 Result :   6

 Element :  8  10  12  14  17
 Result :   4

 Element :  5  8  10  12  14  16  15
 Result :   5

 Element :  1  3  5  7  9  11  13
 Result :   7
#  Python 3 program
#  Find the length of longest arithmetic progression
#  In sorted data
class ArithmeticProgression :
	# Display the elements of array
	def print_data(self, data, size) :
		print("\n Element :", end = "")
		i = 0
		while (i < size) :
			print("  ", data[i], end = "")
			i += 1
		
	
	# returns the maximum of given two numbers
	def max_num(self, a, b) :
		if (a > b) :
			# When (a) is greater
			return a
		
		# When b is greater than or equal to a
		return b
	
	# returns the length of longest arithmetic progression  
	def length_of_longest_ap(self, data, size) :
		# Display given element
		self.print_data(data, size)
		print("\n Result : ", end = "")
		if (size <= 2) :
			# When have two or less than 2 elements
			print("  ", size ,"\n", end = "")
			return
		
		# Minimum 2 result are possible
		result = 2
		# Create storage to calculate result
		auxiliary =[[0 for x in range(size)] for y in range(size)] 

		# Loop controlling variables
		i = 0
		j = 0
		k = 0
		# Set initial value of created storage
		i = 0
		while (i < size) :
			#  Set the [i] row and last column value is to 2
			auxiliary[i][size - 1] = 2
			i += 1
		
		#  Get last-1 position of given data
		j = size - 2
		while (j >= 1) :
			k = j + 1
			i = j - 1
			while (i >= 0 and k <= size - 1) :
				if (data[i] + data[k] < 2 * data[j]) :
					k += 1
				
				elif(data[i] + data[k] > 2 * data[j]) :
					auxiliary[i][j] = 2
					i -= 1
				else :
					auxiliary[i][j] = auxiliary[j][k] + 1
					# Get result
					result = self.max_num(result, auxiliary[i][j])
					k += 1
					i -= 1
				
			
			while (i >= 0) :
				auxiliary[i][j] = 2
				i -= 1
			
			j -= 1
		
		print("  ", result ,"\n", end = "")
	

def main() :
	obj = ArithmeticProgression()
	# Define the collection of sorted integer values
	# This is test inputs
	data1 = [-3, 0, 3, 7, 9, 12, 14, 15, 19, 21, 27]
	data2 = [8, 10, 12, 14, 17]
	data3 = [5, 8, 10, 12, 14, 16, 15]
	data4 = [1, 3, 5, 7, 9, 11, 13]
	# Get the size of given data1
	size = len(data1)
	obj.length_of_longest_ap(data1, size)
	# Get the size of given data2
	size = len(data2)
	obj.length_of_longest_ap(data2, size)
	# Get the size of given data3
	size = len(data3)
	obj.length_of_longest_ap(data3, size)
	# Get the size of given data4
	size = len(data4)
	obj.length_of_longest_ap(data4, size)

if __name__ == "__main__": main()

Output

 Element :   -3   0   3   7   9   12   14   15   19   21   27
 Result :    6

 Element :   8   10   12   14   17
 Result :    4

 Element :   5   8   10   12   14   16   15
 Result :    5

 Element :   1   3   5   7   9   11   13
 Result :    7
#  Ruby program
#  Find the length of longest arithmetic progression
#  In sorted data
class ArithmeticProgression

	# Display the elements of array
	def print_data(data, size)
	
		print("\n Element :")
		i = 0
		while (i < size)
		
			print("  ", data[i])
			i += 1
		end
	end
	# returns the maximum of given two numbers
	def max_num(a, b)
	
		if (a > b)
		
			# When (a) is greater
			return a
		end
		# When b is greater than or equal to a
		return b
	end
	# returns the length of longest arithmetic progression  
	def length_of_longest_ap(data, size)
	
		# Display given element
		self.print_data(data, size)
		print("\n Result : ")
		if (size <= 2)
		
			# When have two or less than 2 elements
			print("  ", size ,"\n")
			return
		end
		# Minimum 2 result are possible
		result = 2
		# Create storage to calculate result
		auxiliary = Array.new(size) {Array.new(size){0}}
		# Loop controlling variables
		i = 0
		j = 0
		k = 0
		# Set initial value of created storage
		i = 0
		while (i < size)
		
			#  Set the [i] row and last column value is to 2
			auxiliary[i][size - 1] = 2
			i += 1
		end
		#  Get last-1 position of given data
		j = size - 2
		while (j >= 1)
		
			k = j + 1
			i = j - 1
			while (i >= 0 && k <= size - 1)
			
				if (data[i] + data[k] < 2 * data[j])
				
					k += 1
				elsif(data[i] + data[k] > 2 * data[j])
				
					auxiliary[i][j] = 2
					i -= 1
				else
				
					auxiliary[i][j] = auxiliary[j][k] + 1
					# Get result
					result = self.max_num(result, auxiliary[i][j])
					k += 1
					i -= 1
				end
			end
			while (i >= 0)
			
				auxiliary[i][j] = 2
				i -= 1
			end
			j -= 1
		end
		print("  ", result ,"\n")
	end
end
def main()

	obj = ArithmeticProgression.new()
	# Define the collection of sorted integer values
	# This is test inputs
	data1 = [-3, 0, 3, 7, 9, 12, 14, 15, 19, 21, 27]
	data2 = [8, 10, 12, 14, 17]
	data3 = [5, 8, 10, 12, 14, 16, 15]
	data4 = [1, 3, 5, 7, 9, 11, 13]
	# Get the size of given data1
	size = data1.length
	obj.length_of_longest_ap(data1, size)
	# Get the size of given data2
	size = data2.length
	obj.length_of_longest_ap(data2, size)
	# Get the size of given data3
	size = data3.length
	obj.length_of_longest_ap(data3, size)
	# Get the size of given data4
	size = data4.length
	obj.length_of_longest_ap(data4, size)
end
main()

Output

 Element :  -3  0  3  7  9  12  14  15  19  21  27
 Result :   6

 Element :  8  10  12  14  17
 Result :   4

 Element :  5  8  10  12  14  16  15
 Result :   5

 Element :  1  3  5  7  9  11  13
 Result :   7
// Scala program
// Find the length of longest arithmetic progression
// In sorted data
class ArithmeticProgression
{
	//Display the elements of array
	def print_data(data: Array[Int], size: Int): Unit = {
		print("\n Element :");
		var i: Int = 0;
		while (i < size)
		{
			print("  " + data(i));
			i += 1;
		}
	}
	//returns the maximum of given two numbers
	def max_num(a: Int, b: Int): Int = {
		if (a > b)
		{
			//When (a) is greater
			return a;
		}
		//When b is greater than or equal to a
		return b;
	}
	//returns the length of longest arithmetic progression  
	def length_of_longest_ap(data: Array[Int], size: Int): Unit = {
		//Display given element
		print_data(data, size);
		print("\n Result : ");
		if (size <= 2)
		{
			//When have two or less than 2 elements
			print("  " + size + "\n");
			return;
		}
		//Minimum 2 result are possible
		var result: Int = 2;
		//Create storage to calculate result
		var auxiliary: Array[Array[Int]] = Array.fill[Int](size,size)(0);
		//Loop controlling variables
		var i: Int = 0;
		var j: Int = 0;
		var k: Int = 0;
		//Set initial value of created storage
		i = 0;
		while (i < size)
		{
			// Set the [i] row and last column value is to 2
			auxiliary(i)(size - 1) = 2;
			i += 1;
		}
		// Get last-1 position of given data
		j = size - 2;
		while (j >= 1)
		{
			k = j + 1;
			i = j - 1;
			while (i >= 0 && k <= size - 1)
			{
				if (data(i) + data(k) < 2 * data(j))
				{
					k += 1;
				}
				else if (data(i) + data(k) > 2 * data(j))
				{
					auxiliary(i)(j) = 2;
					i -= 1;
				}
				else
				{
					auxiliary(i)(j) = auxiliary(j)(k) + 1;
					//Get result
					result = max_num(result, auxiliary(i)(j));
					k += 1;
					i -= 1;
				}
			}
			while (i >= 0)
			{
				auxiliary(i)(j) = 2;
				i -= 1;
			}
			j -= 1;
		}
		print("  " + result + "\n");
	}
}
object Main
{
	def main(args: Array[String]): Unit = {
		var obj: ArithmeticProgression = new ArithmeticProgression();
		//Define the collection of sorted integer values
		//This is test inputs
		var data1: Array[Int] = Array(-3, 0, 3, 7, 9, 12, 14, 15, 19, 21, 27);
		var data2: Array[Int] = Array(8, 10, 12, 14, 17);
		var data3: Array[Int] = Array(5, 8, 10, 12, 14, 16, 15);
		var data4: Array[Int] = Array(1, 3, 5, 7, 9, 11, 13);
		//Get the size of given data1
		var size: Int = data1.length;
		obj.length_of_longest_ap(data1, size);
		//Get the size of given data2
		size = data2.length;
		obj.length_of_longest_ap(data2, size);
		//Get the size of given data3
		size = data3.length;
		obj.length_of_longest_ap(data3, size);
		//Get the size of given data4
		size = data4.length;
		obj.length_of_longest_ap(data4, size);
	}
}

Output

 Element :  -3  0  3  7  9  12  14  15  19  21  27
 Result :   6

 Element :  8  10  12  14  17
 Result :   4

 Element :  5  8  10  12  14  16  15
 Result :   5

 Element :  1  3  5  7  9  11  13
 Result :   7
// Swift program
// Find the length of longest arithmetic progression
// In sorted data
class ArithmeticProgression
{
	//Display the elements of array
	func print_data(_ data: [Int], _ size: Int)
	{
		print("\n Element :", terminator: "");
		var i: Int = 0;
		while (i < size)
		{
			print("  ", data[i], terminator: "");
			i += 1;
		}
	}
	//returns the maximum of given two numbers
	func max_num(_ a: Int, _ b: Int) -> Int
	{
		if (a > b)
		{
			//When (a) is greater
			return a;
		}
		//When b is greater than or equal to a
		return b;
	}
	//returns the length of longest arithmetic progression  
	func length_of_longest_ap(_ data: [Int], _ size: Int)
	{
		//Display given element
		self.print_data(data, size);
		print("\n Result : ", terminator: "");
		if (size <= 2)
		{
			//When have two or less than 2 elements
			print("  ", size ,"\n", terminator: "");
			return;
		}
		//Minimum 2 result are possible
		var result: Int = 2;
		//Create storage to calculate result
		var auxiliary: [[Int]] = Array(repeating : Array( repeating:0 , count:size) ,  count:size);
		//Loop controlling variables
		var i: Int = 0;
		var j: Int = 0;
		var k: Int = 0;
		//Set initial value of created storage
		i = 0;
		while (i < size)
		{
			// Set the [i] row and last column value is to 2
			auxiliary[i][size - 1] = 2;
			i += 1;
		}
		// Get last-1 position of given data
		j = size - 2;
		while (j >= 1)
		{
			k = j + 1;
			i = j - 1;
			while (i >= 0 && k <= size - 1)
			{
				if (data[i] + data[k] < 2 * data[j])
				{
					k += 1;
				}
				else if (data[i] + data[k] > 2 * data[j])
				{
					auxiliary[i][j] = 2;
					i -= 1;
				}
				else
				{
					auxiliary[i][j] = auxiliary[j][k] + 1;
					//Get result
					result = self.max_num(result, auxiliary[i][j]);
					k += 1;
					i -= 1;
				}
			}
			while (i >= 0)
			{
				auxiliary[i][j] = 2;
				i -= 1;
			}
			j -= 1;
		}
		print("  ", result ,"\n", terminator: "");
	}
}
func main()
{
	let obj: ArithmeticProgression = ArithmeticProgression();
	//Define the collection of sorted integer values
	//This is test inputs
	let data1: [Int] = [-3, 0, 3, 7, 9, 12, 14, 15, 19, 21, 27];
	let data2: [Int] = [8, 10, 12, 14, 17];
	let data3: [Int] = [5, 8, 10, 12, 14, 16, 15];
	let data4: [Int] = [1, 3, 5, 7, 9, 11, 13];
	//Get the size of given data1
	var size: Int = data1.count;
	obj.length_of_longest_ap(data1, size);
	//Get the size of given data2
	size = data2.count;
	obj.length_of_longest_ap(data2, size);
	//Get the size of given data3
	size = data3.count;
	obj.length_of_longest_ap(data3, size);
	//Get the size of given data4
	size = data4.count;
	obj.length_of_longest_ap(data4, size);
}
main();

Output

 Element :   -3   0   3   7   9   12   14   15   19   21   27
 Result :    6

 Element :   8   10   12   14   17
 Result :    4

 Element :   5   8   10   12   14   16   15
 Result :    5

 Element :   1   3   5   7   9   11   13
 Result :    7


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