代码

void sort(int *arr, int len) {
  int buf[100000000];
  int t[4][256];
  int i, j;
  int local[256];
  int *a = arr;
  int *b = buf;
  int loc;
  int *c;
  memset(t, 0, sizeof(t));
  for(i = 0; i < 4; ++i) {
    for(j = 0; j < len; ++j) {
      ++t[i][(arr[j] >> (i << 3)) & 255];
    }
  }
  for(i = 0; i < 4; ++i) {
    loc = -1;
    for(j = 0; j < 256; ++j) {
      local[j] = loc;
      loc += t[i][j];
    }
    for(j = 0; j < len; ++j) {
      b[++local[(a[j] >> (i << 3)) & 255]] = a[j];
    }
    c = a;
    a = b;
    b = c;
  }
  return;
}

评测结果