代码

void swap(unsigned *a, unsigned *b)
{
	unsigned t = *a; *a = *b; *b = t;
}
const int BIT = 16;
const int U = 65536;
unsigned b[1000010],y[100000010];
inline int get(int a, int k)
{
    return (a >> (k * BIT)) & (U - 1);
}
 
void sort(unsigned *a, int n)
{
    int i, k;
    for(k = 0; k < 2; k++)
    {
        for(i = 0; i < U; i++) b[i] = 0;
        for(i = 0; i < n; i++) b[get(a[i], k)]++;
        for(i = 1; i < U; i++) b[i] += b[i - 1];
        for(i = n - 1; i >= 0; i--) y[--b[get(a[i], k)]] = a[i];
        swap(a, y);
    }
}

评测结果