Radix Sort

#include <limits.h>

void countSort(int* p, int* res, int l, int k)
{
    k*=8;
    int mask = 255 << k;
    int* ar = new int[257];
    for(int i = 0;i<257;++i)
        ar[i] = 0;
    ++ar;
    for(int i = 0;i<l;++i)
        ar[(p[i]&mask)>>k]++;
    for(int i = 0;i<255;++i)
        ar[i+1] += ar[i];
    --ar;
    for(int i = 0;i<l;++i)
    {
        res[ar[(p[i]&mask)>>k]] = p[i];
        ++ar[(p[i]&mask)>>k];
    }
}

void radixSort(int* p,int l)
{
    int* t = new int[l];
    countSort(p,t,l,0);
    countSort(t,p,l,1);
    countSort(p,t,l,2);
    countSort(t,p,l,3);
}