Efficient program to calculate e^x
The value of Exponential Function e^x can be expressed using following Taylor Series.
e^x = 1 + x/1! + x^2/2! + x^3/3! + ......
How to efficiently calculate the sum of above series?
The series can be re-written as
e^x = 1 + (x/1) (1 + (x/2) (1 + (x/3) (........) ) )
Let the sum needs to be calculated for n terms, we can calculate sum using following loop.
for (i = n - 1, sum = 1; i > 0; --i )
sum = 1 + x * sum / i;
Following is implementation of the above idea.
C++
#include <bits/stdc++.h>
using namespace std;
float exponential( int n, float x)
{
float sum = 1.0f;
for ( int i = n - 1; i > 0; --i )
sum = 1 + x * sum / i;
return sum;
}
int main()
{
int n = 10;
float x = 1.0f;
cout << "e^x = " << fixed << setprecision(5) << exponential(n, x);
return 0;
}
|
C
#include <stdio.h>
float exponential( int n, float x)
{
float sum = 1.0f;
for ( int i = n - 1; i > 0; --i )
sum = 1 + x * sum / i;
return sum;
}
int main()
{
int n = 10;
float x = 1.0f;
printf ( "e^x = %f" , exponential(n, x));
return 0;
}
|
Java
import java.io.*;
class GFG
{
static float exponential( int n, float x)
{
float sum = 1 ;
for ( int i = n - 1 ; i > 0 ; --i )
sum = 1 + x * sum / i;
return sum;
}
public static void main (String[] args)
{
int n = 10 ;
float x = 1 ;
System.out.println( "e^x = " +exponential(n,x));
}
}
|
Python3
def exponential(n, x):
sum = 1.0
for i in range (n, 0 , - 1 ):
sum = 1 + x * sum / i
print ( "e^x =" , sum )
n = 10
x = 1.0
exponential(n, x)
|
C#
using System;
class GFG
{
static float exponential( int n, float x)
{
float sum = 1;
for ( int i = n - 1; i > 0; --i )
sum = 1 + x * sum / i;
return sum;
}
public static void Main ()
{
int n = 10;
float x = 1;
Console.Write( "e^x = " + exponential(n, x));
}
}
|
PHP
<?php
function exponential( $n , $x )
{
$sum = 1.0;
for ( $i = $n - 1; $i > 0; -- $i )
$sum = 1 + $x * $sum / $i ;
return $sum ;
}
$n = 10;
$x = 1.0;
echo ( "e^x = " . exponential( $n , $x ));
?>
|
Javascript
<script>
function exponential(n , x) {
var sum = 1;
for (i = n - 1; i > 0; --i)
sum = 1 + x * sum / i;
return sum;
}
var n = 10;
var x = 1;
document.write( "e^x = " + exponential(n, x).toFixed(6));
</script>
|
Output:
e^x = 2.718282
Time Complexity: O(n)
Auxiliary Space: O(1), since no extra space has been taken.
This article is compiled by Rahul and reviewed by GeeksforGeeks team.
Last Updated :
18 Jul, 2022
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