Factorials of large numbers

Given an integer N, find its factorial.

Example 1:

Input: N = 5
Output: 120
Explanation : 5! = 1*2*3*4*5 = 120


Example 2:

Input: N = 10
Output: 3628800
Explanation :
10! = 1*2*3*4*5*6*7*8*9*10 = 3628800

Example 3:

Input: N = 30
Output:  .
Explanation :
30! =    

Note: Factorials of  can't be stored even in a  long long variable. Big integers must be used for such calculations. Languages like Java, Python, Ruby etc. can handle big integers, but we need to write additional code in C/C++ to handle huge values.

We recommend solving this challenge using BigIntegers.

c++ implementation:

int multiply(int x,int a[],int size)

{

    int carry=0;

    for(int i=0;i<size;i++)

    {

        int p=(a[i]*x)+carry;

        a[i]=p%10;

        carry=p/10;

        

    }

    

    while(carry)

    {

        a[size]=carry%10;

        carry=carry/10;

        size=size+1;

        

    }

    return size;

}

void extraLongFactorials(int n) 

{

    int a[10000];

    a[0]=1;

    int size=1;

    

    for(int i=2;i<=n;i++)

    {

        size=multiply(i,a,size);

    }

    

    for(int i=size-1;i>=0;i--)

    cout<<a[i];

}

 


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