代码

#include <string.h>
#include <algorithm>
unsigned *b;
unsigned buc[3][2048];
void sort(unsigned *a, int n)
{
    b = new unsigned[n];
    for (int i = 0; i < n; ++i)
    {
        ++buc[0][a[i] & 2047];
        ++buc[1][(a[i] >> 11) & 2047];
        ++buc[2][a[i] >> 22];
    }
    for (unsigned k = 0; k < 3; ++k)
    {
        unsigned offset = 0, lim = (k == 2) ? 1024 : 2048;
        for (unsigned i = 0; i < lim; ++i) 
            std::swap(buc[k][i], offset), offset += buc[k][i];
    }
    for (unsigned i = 0; i < n; ++i) b[buc[0][a[i] & 2047]++] = a[i];
    for (unsigned i = 0; i < n; ++i) a[buc[1][(b[i] >> 11) & 2047]++] = b[i];
    for (unsigned i = 0; i < n; ++i) b[buc[2][a[i] >> 22]++] = a[i];
    memcpy(a, b, n << 2);
}

评测结果