3 ways to find the exponent without using pow() method in C++

How to find the exponent without using pow() method in C++:

We can find the exponent without using the pow() method in C++. We can use a loop or a recursive method. To find a^b, we have to multiply a with itself for b number of times.

In this post, we will learn how to calculate the exponent by using a for loop, while loop and with a recursive method.

Example 1: C++ program find the exponent by using for loops:

The below program uses for loops to find the exponent value. It takes two numbers as inputs from the user and finds the exponent using a for loop.

#include <iostream>
using namespace std;

long power(long b, long e)
{
    long p = 1;

    for (int i = 0; i < e; i++)
    {
        p *= b;
    }

    return p;
}

int main()
{
    long b, e;

    cout << "Enter the base: " << endl;
    cin >> b;

    cout << "Enter the exponent: " << endl;
    cin >> e;

    cout << b << "^" << e << "=" << power(b, e) << endl;
}

In this example,

The base and exponent values are stored in b and e variables. Both are long variables.
The power method takes the base and exponent values as its arguments.
- It uses a for loop to find the power. Variable p is used to hold the power. It is initialized as 1.
- The for loop runs for e number of times and on each iteration, it multiplies current value of p with b and save that value in p.
- Once the loop ends, p will hold the value of the required exponent.

It will give output as like below:

Enter the base: 
3
Enter the exponent: 
4
3^4=81

Enter the base: 
22
Enter the exponent: 
0
22^0=1

Example 2: C++ program find the exponent by using while loops:

We can also write the above program using while loops. It will work similarly.

#include <iostream>
using namespace std;

long power(long b, long e)
{
    long p = 1;

    while(e--){
        p *= b;
    }

    return p;
}

int main()
{
    long b, e;

    cout << "Enter the base: " << endl;
    cin >> b;

    cout << "Enter the exponent: " << endl;
    cin >> e;

    cout << b << "^" << e << "=" << power(b, e) << endl;
}

On each iteration of the loop, it decrements the value of e by 1 and multiplies b to the current value of p. Once the while loop ends, p will hold the exponential value.

It will give similar output.

Example 3: C++ program find the exponent recursively:

A recursive method calls itself again and again till it finds a result. We can find the exponent value by using a recursive method. The below program uses a recursive method to find the exponent:

#include <iostream>
using namespace std;

long power(long b, long e, long p)
{
    if (e == 0)
        return p;

    return power(b, e - 1, p * b);
}

int main()
{
    long b, e;

    cout << "Enter the base: " << endl;
    cin >> b;

    cout << "Enter the exponent: " << endl;
    cin >> e;

    cout << b << "^" << e << "=" << power(b, e, 1) << endl;
}

power is a recursive method. It takes the base, exponent and also result as its arguments.
On first call, we are passing p as 1.
It calls itself again with updated b, e and p values.
It returns the value of p once e become 0. On each iteration, the value of e is decremented by 1.

It will give similar result.

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Updated on 19 Jun 2022

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