代码

#include <bits/stdc++.h>

unsigned b[100000000], B[256]; 
void sort(unsigned *a, int n) {
  memset(B, 0, sizeof(B)); 
  for(int i = 0; i < n; i++) B[a[i] & 255]++; 
  for(int i = 1; i <= 255; i++) B[i] += B[i - 1];
  for(int i = n - 1; i >= 0; i--) b[B[a[i] & 255]--] = a[i]; 
  memset(B, 0, sizeof(B)); 
  for(int i = 0; i < n; i++) B[(b[i] >> 8) & 255]++; 
  for(int i = 1; i <= 255; i++) B[i] += B[i - 1]; 
  for(int i = n - 1; i >= 0; i--) a[B[(b[i] >> 8) & 255]--] = b[i];
  memset(B, 0, sizeof(B)); 
  for(int i = 0; i < n; i++) B[(a[i] >> 16) & 255]++; 
  for(int i = 1; i <= 255; i++) B[i] += B[i - 1];
  for(int i = n - 1; i >= 0; i--) b[B[(a[i] >> 16) & 255]--] = a[i]; 
  memset(B, 0, sizeof(B)); 
  for(int i = 0; i < n; i++) B[(b[i] >> 24) & 255]++; 
  for(int i = 1; i <= 255; i++) B[i] += B[i - 1]; 
  for(int i = n - 1; i >= 0; i--) a[B[(b[i] >> 24) & 255]--] = b[i];
}

评测结果