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C++ Program to Find Factorial
Factorial of a non-negative integer n is the product of all the positive integers that are less than or equal to n.
For example: The factorial of 5 is 120.
5! = 5 * 4 * 3 * 2 *1 5! = 120
The factorial of an integer can be found using a recursive program or a non-recursive program. Example of both of these are given as follows.
Factorial using Non-Recursive Program
A for loop can be used to find the factorial of a number. This is demonstrated using the following program −
Example
#include <iostream>
using namespace std;
int main() {
int n = 5, fact = 1, i;
for(i=1; i<=n; i++)
fact = fact * i;
cout<<"Factorial of "<<n<<" is "<<fact;
return 0;
}Output
Factorial of 5 is 120
In the above program, the for loop runs from 1 to n. For each iteration of the loop, fact is multiplied with i. The final value of fact is the product of all numbers from 1 to n. This is demonstrated using the following code snippet.
for(i=1; i<=n; i++) fact = fact * i;
Factorial Using a Recursive Program
The following program demonstrates a recursive program to find the factorial of a number.
Example
#include <iostream>
using namespace std;
int fact(int n) {
if ((n==0)||(n==1))
return 1;
else
return n*fact(n-1);
}
int main() {
int n = 5;
cout<<"Factorial of "<<n<<" is "<<fact(n);
return 0;
}Output
Factorial of 5 is 120
In the above program, the function fact() is a recursive function. The main() function calls fact() using the number whose factorial is required. This is demonstrated by the following code snippet.
cout<<"Factorial of "<<n<<" is "<<fact(n);
If the number is 0 or 1, then fact() returns 1. If the number is any other, then fact() recursively calls itself with the value n-1.
This is demonstrated using the following code snippet −
int fact(int n) {
if ((n==0)||(n==1))
return 1;
else
return n*fact(n-1);
}
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