gistfile1.cpp

uint32_t FindMissing(uint32_t* arr) {
  uint32_t res[4];
  __m128i c = _mm_set1_epi32(0);
 
  for (int i = 0; i < 100; i+=4) {
    c = _mm_add_epi32(c,
      _mm_loadu_si128((__m128i*)&arr[i]));
  }
 
  _mm_store_si128((__m128i*)res, c);
  return 5050 - res[0] - res[1] - res[2] - res[3];
}