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29 changes: 29 additions & 0 deletions PrimalityTest/c++/SEGSEIVE.CPP
Original file line number Diff line number Diff line change
@@ -0,0 +1,29 @@
// This functions finds all primes smaller than 'limit'
// using simple sieve of eratosthenes.
void simpleSieve(int limit)
{
// Create a boolean array "mark[0..limit-1]" and
// initialize all entries of it as true. A value
// in mark[p] will finally be false if 'p' is Not
// a prime, else true.
bool mark[limit];
memset(mark, true, sizeof(mark));

// One by one traverse all numbers so that their
// multiples can be marked as composite.
for (int p=2; p*p<limit; p++)
{
// If p is not changed, then it is a prime
if (mark[p] == true)
{
// Update all multiples of p
for (int i=p*2; i<limit; i+=p)
mark[i] = false;
}
}

// Print all prime numbers and store them in prime
for (int p=2; p<limit; p++)
if (mark[p] == true)
cout << p << " ";
}
73 changes: 73 additions & 0 deletions Sorting/Radix sort/RADIXSOR.CPP
Original file line number Diff line number Diff line change
@@ -0,0 +1,73 @@
// C++ implementation of Radix Sort
#include<iostream>
using namespace std;

// A utility function to get maximum value in arr[]
int getMax(int arr[], int n)
{
int mx = arr[0];
for (int i = 1; i < n; i++)
if (arr[i] > mx)
mx = arr[i];
return mx;
}

// A function to do counting sort of arr[] according to
// the digit represented by exp.
void countSort(int arr[], int n, int exp)
{
int output[n]; // output array
int i, count[10] = {0};

// Store count of occurrences in count[]
for (i = 0; i < n; i++)
count[ (arr[i]/exp)%10 ]++;

// Change count[i] so that count[i] now contains actual
// position of this digit in output[]
for (i = 1; i < 10; i++)
count[i] += count[i - 1];

// Build the output array
for (i = n - 1; i >= 0; i--)
{
output[count[ (arr[i]/exp)%10 ] - 1] = arr[i];
count[ (arr[i]/exp)%10 ]--;
}

// Copy the output array to arr[], so that arr[] now
// contains sorted numbers according to current digit
for (i = 0; i < n; i++)
arr[i] = output[i];
}

// The main function to that sorts arr[] of size n using
// Radix Sort
void radixsort(int arr[], int n)
{
// Find the maximum number to know number of digits
int m = getMax(arr, n);

// Do counting sort for every digit. Note that instead
// of passing digit number, exp is passed. exp is 10^i
// where i is current digit number
for (int exp = 1; m/exp > 0; exp *= 10)
countSort(arr, n, exp);
}

// A utility function to print an array
void print(int arr[], int n)
{
for (int i = 0; i < n; i++)
cout << arr[i] << " ";
}

// Driver program to test above functions
int main()
{
int arr[] = {170, 45, 75, 90, 802, 24, 2, 66};
int n = sizeof(arr)/sizeof(arr[0]);
radixsort(arr, n);
print(arr, n);
return 0;
}