fermat_test.cpp

#include<bits/stdc++.h>
using namespace std;
#define ll long long int
#define sf scanf
#define pf printf
long long int binarySearch(long long int arr[],long long  int l, long long int r, long long int x)
{
  while (l <= r)
  {
    long long int m = l + (r-l)/2;

    if (arr[m] == x) return m;  // Check if x is present at mid

    if (arr[m] < x) l = m + 1; // If x greater, ignore left half

    else r = m - 1; // If x is smaller, ignore left half
  }
  return -1; // if we reach here, then element was not present
}
void merge(long long int arr[], long long int l, long long int m, long long int r)
{
    long long int i, j, k;
    long long int n1 = m - l + 1;
    long long int n2 =  r - m;

    /* create temp arrays */
   long long  int L[n1], R[n2];

    /* Copy data to temp arrays L[] and R[] */
    for(i = 0; i < n1; i++)
        L[i] = arr[l + i];
    for(j = 0; j < n2; j++)
        R[j] = arr[m + 1+ j];

    /* Merge the temp arrays back into arr[l..r]*/
    i = 0;
    j = 0;
    k = l;
    while (i < n1 && j < n2)
    {
        if (L[i] <= R[j])
        {
            arr[k] = L[i];
            i++;
        }
        else
        {
            arr[k] = R[j];
            j++;
        }
        k++;
    }

    /* Copy the remaining elements of L[], if there are any */
    while (i < n1)
    {
        arr[k] = L[i];
        i++;
        k++;
    }

    /* Copy the remaining elements of R[], if there are any */
    while (j < n2)
    {
        arr[k] = R[j];
        j++;
        k++;
    }
}

/* l is for left index and r is right index of the sub-array
  of arr to be sorted */
void mergeSort(long long int arr[], long long int l, long long int r)
{
    if (l < r)
    {
        long long  int m = l+(r-l)/2;//Same as (l+r)/2, but avoids overflow for large l and h
        mergeSort(arr, l, m);
	    mergeSort(arr, m+1, r);
        merge(arr, l, m, r);
    }
}
void printArray(long long int A[], long long int size)
{
   long long  int i;
    for (i=0; i < size; i++)
        printf("%lld ", A[i]);
    printf("\n");
}

int power(int a, unsigned int n, int p)
{
    int res = 1; 
    a = a % p;  
 
    while (n > 0)
    {
        if (n & 1)
            res = (res*a) % p;
        n = n>>1; 
        a = (a*a) % p;
    }
    return res;
}
bool isPrime(unsigned int n, int k)
{
   if (n <= 1 || n == 4)  return false;
   if (n <= 3) return true;
   while (k>0)
   {
       int a = 2 + rand()%(n-4);  
       if (power(a, n-1, n) != 1)
          return false;
 
       k--;
    }
 
    return true;
}
int main()
{
    int k=5,n;
    cin>>n;
    isPrime(n, k)?  cout << "true\n": cout << " false\n";
    return 0;
}