Find the sum of the following sequence : 2, 22, 222, ……… to n terms.
Examples :
Input : 2 Output: 23.99868 Input : 3 Output: 245.98647
A simple solution is to compute terms one by one and add to the result.
The above problem can be efficiently solved using the following formula:
C++14
// CPP program to find sum of series // 2, 22, 222, .. #include <bits/stdc++.h> using namespace std;
// function which return the // the sum of series float sumOfSeries( int n)
{ return 0.02469 * (10*( pow (10, n) - 1)- (9 * n));
} // driver code int main()
{ int n = 3;
cout << sumOfSeries(n);
return 0;
} |
Java
// JAVA Code for Sum of the // sequence 2, 22, 222,... import java.util.*;
class GFG {
// function which return the
// the sum of series
static double sumOfSeries( int n)
{
return 0.02469 * (( 10 *Math.pow( 10 , n)
- 1 ) - ( 9 * n));
}
/* Driver program */
public static void main(String[] args)
{
int n = 3 ;
System.out.println(sumOfSeries(n));
}
} // This code is contributed by Arnav Kr. Mandal. |
Python3
# Python3 code to find # sum of series # 2, 22, 222, .. import math
# function which return # the sum of series def sumOfSeries( n ):
return 0.02469 * (( 10 * math. pow ( 10 , n) - 1 ) - ( 9 * n))
# driver code n = 3
print ( sumOfSeries(n))
# This code is contributed by "Sharad_Bhardwaj". |
C#
// C# Code for Sum of the // sequence 2, 22, 222,... using System;
class GFG {
// Function which return the
// the sum of series
static double sumOfSeries( int n)
{
return 0.02469 * ((10*Math.Pow(10, n)
- 1) - (9 * n));
}
// Driver Code
public static void Main()
{
int n = 3;
Console.Write(sumOfSeries(n));
}
} // This code is contributed by vt_m. |
PHP
<?php // PHP program to find sum // of series 2, 22, 222, .. // function which return the // the sum of series function sumOfSeries( $n )
{ return 0.02469 * ((10*pow(10, $n ) -
1 )- (9 * $n ));
} // Driver Code $n = 3;
echo (sumOfSeries( $n ));
// This code is contributed by Ajit. ?> |
Javascript
<script> // JavaScript program for Sum of the // sequence 2, 22, 222,... // function which return the
// the sum of series
function sumOfSeries(n)
{
return 0.0246 * ((10*Math.pow(10, n)
- 1) - (9 * n));
}
// Driver code let n = 3;
document.write(sumOfSeries(n));
</script> |
Output
245.986
Time complexity: O(log n) since using inbuilt power function.
Auxiliary Space: O(1)