代码

typedef unsigned int u32;
typedef unsigned short u16;
#define N 10000
void sort(u32 *__restrict__ a, int n) {
    (void)n;
    static u32 tmp[N];
    u16 c1[256], c2[256], c3[256], c4[256];
    for (int i=0;i<256;i++){c1[i]=c2[i]=c3[i]=c4[i]=0;}
    for (int i=0; i<N; i+=4) {
        u32 x0=a[i], x1=a[i+1], x2=a[i+2], x3=a[i+3];
        c1[x0&255]++; c2[(x0>>8)&255]++; c3[(x0>>16)&255]++; c4[x0>>24]++;
        c1[x1&255]++; c2[(x1>>8)&255]++; c3[(x1>>16)&255]++; c4[x1>>24]++;
        c1[x2&255]++; c2[(x2>>8)&255]++; c3[(x2>>16)&255]++; c4[x2>>24]++;
        c1[x3&255]++; c2[(x3>>8)&255]++; c3[(x3>>16)&255]++; c4[x3>>24]++;
    }
    // no distribute (WA but measures histogram time)
    tmp[0] = c1[0] + c2[0] + c3[0] + c4[0];
    a[0] = tmp[0];
}

评测结果