代码

#include<algorithm>

constexpr int B=8;
constexpr int msk=(1<<B)-1;
unsigned b[1<<27];
int cnt[1<<B];

void sort(unsigned *a, int n) {
    unsigned *r=a;
    unsigned *b=::b;
    for(int p=0;p<32;p+=B){
        for(int i=0;i<(1<<B);++i)cnt[i]=0;
        for(int i=0;i<n;++i)cnt[a[i]>>p&msk]++;
        for(int i=1;i<(1<<B);++i)cnt[i]+=cnt[i-1];
        for(int i=n-1;~i;--i)b[--cnt[a[i]>>p&msk]]=a[i];
        std::swap(a,b);
    }
    if(a!=r)std::copy(a,a+n,r);
}

评测结果