Factorial of Large Number in C and C++

Here you will get program to find factorial of large number in C and C++.

Factorial of big numbers contain so many digits. For example factorial of 100 has almost 158 digits. So there is no data type available to store such a long value. But we can find factorial for large numbers using simple multiplication method that we used in our school time. Below I have shared the program for it.

Program for Factorial of Large Number in C

#include<stdio.h>
     
int multiply(int x,int a[],int size)
{
	int carry=0,i,p;
    
	for(i=0;i<size;++i)
	{
		p=a[i]*x+carry;
		a[i]=p%10;
		carry=p/10;
	}
		
	while(carry!=0)
	{
		a[size]=carry%10;
		carry=carry/10;
		size++;		
	}    	
    	return size;
}
     
int main()
{  
	int n,a[1000],i,size=1;
    a[0]=1;

	printf("Enter any large number:");
    scanf("%d",&n);
    	
    for(i=2;i<=n;++i) {
		size=multiply(i,a,size);    		
    }
    	
    for(i=size-1;i>=0;--i)
    {
		printf("%d",a[i]);    	
    }
    	
   	return 0;
}

Program for Factorial of Large Number in C++

#include<iostream>

using namespace std;

int multiply(int x,int a[],int size)
{
	int carry=0,i,p;
    
	for(i=0;i<size;++i)
	{
		p=a[i]*x+carry;
		a[i]=p%10;
		carry=p/10;
	}
		
	while(carry!=0)
	{
		a[size]=carry%10;
		carry=carry/10;
		size++;		
	}    	
    	return size;
}
     
int main()
{  
	int n,a[1000],i,size=1;
    a[0]=1;

	cout<<"Enter any large number:";
    cin>>n;
    	
    for(i=2;i<=n;++i) {
		size=multiply(i,a,size);    		
    }
    	
    for(i=size-1;i>=0;--i)
    {
		cout<<a[i];    	
    }
    	
   	return 0;
}

Output

If you have any doubt regarding above program then you can ask it by commenting below.

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