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Write a program to calculate pow(x,n)
  • Difficulty Level : Easy
  • Last Updated : 13 Apr, 2021
 

Given two integers x and n, write a function to compute xn. We may assume that x and n are small and overflow doesn’t happen.

Image

Examples : 

Input : x = 2, n = 3
Output : 8

Input : x = 7, n = 2
Output : 49
 

Below solution divides the problem into subproblems of size y/2 and call the subproblems recursively. 

C++




// C++ program to calculate pow(x,n)
#include<iostream>
using namespace std;
class gfg
{
     
/* Function to calculate x raised to the power y */
public:
int power(int x, unsigned int y)
{
    if (y == 0)
        return 1;
    else if (y % 2 == 0)
        return power(x, y / 2) * power(x, y / 2);
    else
        return x * power(x, y / 2) * power(x, y / 2);
}
};
 
/* Driver code */
int main()
{
    gfg g;
    int x = 2;
    unsigned int y = 3;
 
    cout << g.power(x, y);
    return 0;
}
 
// This code is contributed by SoM15242
C



#include<stdio.h>
 
/* Function to calculate x raised to the power y */
int power(int x, unsigned int y)
{
    if (y == 0)
        return 1;
    else if (y%2 == 0)
        return power(x, y/2)*power(x, y/2);
    else
        return x*power(x, y/2)*power(x, y/2);
}
 
/* Program to test function power */
int main()
{
    int x = 2;
    unsigned int y = 3;
 
    printf("%d", power(x, y));
    return 0;
}
Java



class GFG {
    /* Function to calculate x raised to the power y */
    static int power(int x, int y)
    {
        if (y == 0)
            return 1;
        else if (y % 2 == 0)
            return power(x, y / 2) * power(x, y / 2);
        else
            return x * power(x, y / 2) * power(x, y / 2);
    }
 
    /* Program to test function power */
    public static void main(String[] args)
    {
        int x = 2;
        int y = 3;
 
        System.out.printf("%d", power(x, y));
    }
}
 
// This code is contributed by Smitha Dinesh Semwal
Python3



# Python3 program to calculate pow(x,n)
 
# Function to calculate x
# raised to the power y
def power(x, y):
 
    if (y == 0): return 1
    elif (int(y % 2) == 0):
        return (power(x, int(y / 2)) *
               power(x, int(y / 2)))
    else:
        return (x * power(x, int(y / 2)) *
                   power(x, int(y / 2)))
 
# Driver Code
x = 2; y = 3
print(power(x, y))
 
# This code is contributed by Smitha Dinesh Semwal.
C#



using System;
 
public class GFG {
     
    // Function to calculate x raised to the power y
    static int power(int x, int y)
    {
        if (y == 0)
            return 1;
        else if (y % 2 == 0)
            return power(x, y / 2) * power(x, y / 2);
        else
            return x * power(x, y / 2) * power(x, y / 2);
    }
 
    // Program to test function power
    public static void Main()
    {
        int x = 2;
        int y = 3;
 
        Console.Write(power(x, y));
    }
}
 
// This code is contributed by shiv_bhakt.
PHP



<?php
// Function to calculate x
// raised to the power y
function power($x, $y)
{
    if ($y == 0)
        return 1;
    else if ($y % 2 == 0)
        return power($x, (int)$y / 2) *
               power($x, (int)$y / 2);
    else
        return $x * power($x, (int)$y / 2) *
                    power($x, (int)$y / 2);
}
 
// Driver Code
$x = 2;
$y = 3;
 
echo power($x, $y);
     
// This code is contributed by ajit
?>
Javascript



<script>
// Javascript program to calculate pow(x,n)
 
// Function to calculate x
// raised to the power y
function power(x, y)
{
    if (y == 0)
        return 1;
    else if (y % 2 == 0)
        return power(x, parseInt(y / 2, 10)) *
               power(x, parseInt(y / 2, 10));
    else
        return x * power(x, parseInt(y / 2, 10)) *
                   power(x, parseInt(y / 2, 10));
}
 
// Driver code
let x = 2;
let y = 3;
 
document.write(power(x, y));
 
// This code is contributed by mukesh07
 
</script>
Output : 


8
Time Complexity: O(n) 
Space Complexity: O(1) 
Algorithmic Paradigm: Divide and conquer.
Above function can be optimized to O(logn) by calculating power(x, y/2) only once and storing it. 
C++



/* Function to calculate x raised to the power y in O(logn)*/
int power(int x, unsigned int y)
{
    int temp;
    if( y == 0)
        return 1;
    temp = power(x, y / 2);
    if (y % 2 == 0)
        return temp * temp;
    else
        return x * temp * temp;
}
 
// This code is contributed by Shubhamsingh10
C



/* Function to calculate x raised to the power y in O(logn)*/
int power(int x, unsigned int y)
{
    int temp;
    if( y == 0)
        return 1;
    temp = power(x, y/2);
    if (y%2 == 0)
        return temp*temp;
    else
        return x*temp*temp;
}
Java



/* Function to calculate x raised to the power y in O(logn)*/
static int power(int x, int y)
{
    int temp;
    if( y == 0)
        return 1;
    temp = power(x, y / 2);
    if (y % 2 == 0)
        return temp*temp;
    else
        return x*temp*temp;
}
 
// This code is contributed by divyeshrabadiya07.
Python3



# Function to calculate x raised to the power y in O(logn)
def power(x,y):
    temp = 0
    if( y == 0):
        return 1
    temp = power(x, int(y / 2))
    if (y % 2 == 0)
        return temp * temp;
    else
        return x * temp * temp;
 
# This code is contributed by avanitrachhadiya2155
C#



/* Function to calculate x raised to the power y in O(logn)*/
static int power(int x, int y)
{
    int temp;
    if( y == 0)
        return 1;
    temp = power(x, y / 2);
    if (y % 2 == 0)
        return temp*temp;
    else
        return x*temp*temp;
}
 
// This code is contributed by divyesh072019.
Javascript



<script>
 
/* Function to calculate x raised to the power y in O(logn)*/
function power(x , y)
{
    var temp;
    if( y == 0)
        return 1;
    temp = power(x, y / 2);
    if (y % 2 == 0)
        return temp*temp;
    else
        return x*temp*temp;
}
 
// This code is contributed by todaysgaurav
 
</script>
Time Complexity of optimized solution: O(logn) 
Let us extend the pow function to work for negative y and float x. 
C++



/* Extended version of power function
that can work for float x and negative y*/
#include <bits/stdc++.h>
using namespace std;
 
float power(float x, int y)
{
    float temp;
    if(y == 0)
        return 1;
    temp = power(x, y / 2);
    if (y % 2 == 0)
        return temp * temp;
    else
    {
        if(y > 0)
            return x * temp * temp;
        else
            return (temp * temp) / x;
    }
}
 
// Driver Code
int main()
{
    float x = 2;
    int y = -3;
    cout << power(x, y);
    return 0;
}
 
// This is code is contributed
// by rathbhupendra
C



/* Extended version of power function that can work
 for float x and negative y*/
#include<stdio.h>
 
float power(float x, int y)
{
    float temp;
    if( y == 0)
       return 1;
    temp = power(x, y/2);      
    if (y%2 == 0)
        return temp*temp;
    else
    {
        if(y > 0)
            return x*temp*temp;
        else
            return (temp*temp)/x;
    }
} 
 
/* Program to test function power */
int main()
{
    float x = 2;
    int y = -3;
    printf("%f", power(x, y));
    return 0;
}
Java



/* Java code for extended version of power function
that can work for float x and negative y */
class GFG {
     
    static float power(float x, int y)
    {
        float temp;
        if( y == 0)
            return 1;
        temp = power(x, y/2);
         
        if (y%2 == 0)
            return temp*temp;
        else
        {
            if(y > 0)
                return x * temp * temp;
            else
                return (temp * temp) / x;
        }
    }
     
    /* Program to test function power */
    public static void main(String[] args)
    {
        float x = 2;
        int y = -3;
        System.out.printf("%f", power(x, y));
    }
}
 
// This code is contributed by  Smitha Dinesh Semwal.
Python3



# Python3 code for extended version
# of power function that can work
# for float x and negative y
 
def power(x, y):
 
    if(y == 0): return 1
    temp = power(x, int(y / 2))
     
    if (y % 2 == 0):
        return temp * temp
    else:
        if(y > 0): return x * temp * temp
        else: return (temp * temp) / x
     
# Driver Code
x, y = 2, -3
print('%.6f' %(power(x, y)))
 
# This code is contributed by Smitha Dinesh Semwal.
C#



// C# code for extended version of power function
// that can work for float x and negative y
 
using System;
 
public class GFG{
     
    static float power(float x, int y)
    {
        float temp;
         
        if( y == 0)
            return 1;
        temp = power(x, y/2);
         
        if (y % 2 == 0)
            return temp * temp;
        else
        {
            if(y > 0)
                return x * temp * temp;
            else
                return (temp * temp) / x;
        }
    }
     
    // Program to test function power
    public static void Main()
    {
        float x = 2;
        int y = -3;
         
        Console.Write(power(x, y));
    }
}
 
// This code is contributed by shiv_bhakt.
PHP



<?php
// Extended version of power
// function that can work
// for float x and negative y
 
function power($x, $y)
{
    $temp;
    if( $y == 0)
    return 1;
    $temp = power($x, $y / 2);    
    if ($y % 2 == 0)
        return $temp * $temp;
    else
    {
        if($y > 0)
            return $x *
                   $temp * $temp;
        else
            return ($temp *
                    $temp) / $x;
    }
}
 
// Driver Code
$x = 2;
$y = -3;
echo power($x, $y);
 
// This code is contributed by ajit
?>
Javascript



<script>
 
// Javascript code for extended
// version of power function that
// can work for var x and negative y
function power(x, y)
{
    var temp;
     
    if (y == 0)
        return 1;
         
    temp = power(x, parseInt(y / 2));
 
    if (y % 2 == 0)
        return temp * temp;
    else
    {
        if (y > 0)
            return x * temp * temp;
        else
            return (temp * temp) / x;
    }
}
 
// Driver code
var x = 2;
var y = -3;
 
document.write( power(x, y).toFixed(6));
 
// This code is contributed by aashish1995
 
</script>
Output : 
0.125000
Time Complexity: O(log|n|)
Auxiliary Space: O(1)
 
Using recursion:
This approach is almost similar to iterative solution 
Java



// Java program for the above approach
import java.io.*;
 
class GFG {
    public static int power(int x, int y)
    {
         
        // If x^0 return 1
        if (y == 0)
            return 1;
         
        // If we need to find of 0^y
        if (x == 0)
            return 0;
         
        // For all other cases
        return x * power(x, y - 1);
    }
   
    // Driver Code
    public static void main(String[] args)
    {
        int x = 2;
        int y = 3;
 
        System.out.println(power(x, y));
    }
}
C#



// C# program for the above approach
using System;
 
class GFG{
     
public static int power(int x, int y)
{
     
    // If x^0 return 1
    if (y == 0)
        return 1;
     
    // If we need to find of 0^y
    if (x == 0)
        return 0;
     
    // For all other cases
    return x * power(x, y - 1);
}
 
// Driver Code
public static void Main(String[] args)
{
    int x = 2;
    int y = 3;
 
    Console.WriteLine(power(x, y));
}
}
 
// This code is contributed by Rajput-Ji
Javascript



<script>
 
// javascript program for the above approach
    function power(x , y) {
 
        // If x^0 return 1
        if (y == 0)
            return 1;
 
        // If we need to find of 0^y
        if (x == 0)
            return 0;
 
        // For all other cases
        return x * power(x, y - 1);
    }
 
    // Driver Code
     
        var x = 2;
        var y = 3;
 
        document.write(power(x, y));
 
// This code is contributed by Rajput-Ji
 
</script>
Output:
8
Using Math.pow() function of java:
Java



// Java program for the above approach
import java.io.*;
 
class GFG {
    public static int power(int x, int y)
    {
         
        // Math.pow() is a function that
        // return floating number
        return (int)Math.pow(x, y);
    }
   
    // Driver Code
    public static void main(String[] args)
    {
        int x = 2;
        int y = 3;
 
        System.out.println(power(x, y));
    }
}
Javascript



<script>
 
// Javascript program for the above approach
 
    function power( x, y)
    {
         
        // Math.pow() is a function that
        // return floating number
        return parseInt(Math.pow(x, y));
    }
 
    // Driver Code
     
        let x = 2;
        let y = 3;
 
        document.write(power(x, y));
         
// This code is contributed by sravan kumar
 
</script>
Output:
8
Write an iterative O(Log y) function for pow(x, y) 
Modular Exponentiation (Power in Modular Arithmetic)
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