关于利用STL实现哈希的问题

// std::__detail and std::tr1::__detail definitions -*- C++ -*-

// Copyright (C) 2007-2018 Free Software Foundation, Inc.
//
// This file is part of the GNU ISO C++ Library.  This library is free
// software; you can redistribute it and/or modify it under the
// terms of the GNU General Public License as published by the
// Free Software Foundation; either version 3, or (at your option)
// any later version.

// This library is distributed in the hope that it will be useful,
// but WITHOUT ANY WARRANTY; without even the implied warranty of
// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
// GNU General Public License for more details.

// Under Section 7 of GPL version 3, you are granted additional
// permissions described in the GCC Runtime Library Exception, version
// 3.1, as published by the Free Software Foundation.

// You should have received a copy of the GNU General Public License and
// a copy of the GCC Runtime Library Exception along with this program;
// see the files COPYING3 and COPYING.RUNTIME respectively.  If not, see
// <http://www.gnu.org/licenses/>.

namespace __detail
{
  // The sentinel value is kept only for abi backward compatibility.
  extern const unsigned long __prime_list[] = // 256 + 1 or 256 + 48 + 1
  {
    2ul, 3ul, 5ul, 7ul, 11ul, 13ul, 17ul, 19ul, 23ul, 29ul, 31ul,
    37ul, 41ul, 43ul, 47ul, 53ul, 59ul, 61ul, 67ul, 71ul, 73ul, 79ul,
    83ul, 89ul, 97ul, 103ul, 109ul, 113ul, 127ul, 137ul, 139ul, 149ul,
    157ul, 167ul, 179ul, 193ul, 199ul, 211ul, 227ul, 241ul, 257ul,
    277ul, 293ul, 313ul, 337ul, 359ul, 383ul, 409ul, 439ul, 467ul,
    503ul, 541ul, 577ul, 619ul, 661ul, 709ul, 761ul, 823ul, 887ul,
    953ul, 1031ul, 1109ul, 1193ul, 1289ul, 1381ul, 1493ul, 1613ul,
    1741ul, 1879ul, 2029ul, 2179ul, 2357ul, 2549ul, 2753ul, 2971ul,
    3209ul, 3469ul, 3739ul, 4027ul, 4349ul, 4703ul, 5087ul, 5503ul,
    5953ul, 6427ul, 6949ul, 7517ul, 8123ul, 8783ul, 9497ul, 10273ul,
    11113ul, 12011ul, 12983ul, 14033ul, 15173ul, 16411ul, 17749ul,
    19183ul, 20753ul, 22447ul, 24281ul, 26267ul, 28411ul, 30727ul,
    33223ul, 35933ul, 38873ul, 42043ul, 45481ul, 49201ul, 53201ul,
    57557ul, 62233ul, 67307ul, 72817ul, 78779ul, 85229ul, 92203ul,
    99733ul, 107897ul, 116731ul, 126271ul, 136607ul, 147793ul,
    159871ul, 172933ul, 187091ul, 202409ul, 218971ul, 236897ul,
    256279ul, 277261ul, 299951ul, 324503ul, 351061ul, 379787ul,
    410857ul, 444487ul, 480881ul, 520241ul, 562841ul, 608903ul,
    658753ul, 712697ul, 771049ul, 834181ul, 902483ul, 976369ul,
    1056323ul, 1142821ul, 1236397ul, 1337629ul, 1447153ul, 1565659ul,
    1693859ul, 1832561ul, 1982627ul, 2144977ul, 2320627ul, 2510653ul,
    2716249ul, 2938679ul, 3179303ul, 3439651ul, 3721303ul, 4026031ul,
    4355707ul, 4712381ul, 5098259ul, 5515729ul, 5967347ul, 6456007ul,
    6984629ul, 7556579ul, 8175383ul, 8844859ul, 9569143ul, 10352717ul,
    11200489ul, 12117689ul, 13109983ul, 14183539ul, 15345007ul,
    16601593ul, 17961079ul, 19431899ul, 21023161ul, 22744717ul,
    24607243ul, 26622317ul, 28802401ul, 31160981ul, 33712729ul,
    36473443ul, 39460231ul, 42691603ul, 46187573ul, 49969847ul,
    54061849ul, 58488943ul, 63278561ul, 68460391ul, 74066549ul,
    80131819ul, 86693767ul, 93793069ul, 101473717ul, 109783337ul,
    118773397ul, 128499677ul, 139022417ul, 150406843ul, 162723577ul,
    176048909ul, 190465427ul, 206062531ul, 222936881ul, 241193053ul,
    260944219ul, 282312799ul, 305431229ul, 330442829ul, 357502601ul,
    386778277ul, 418451333ul, 452718089ul, 489790921ul, 529899637ul,
    573292817ul, 620239453ul, 671030513ul, 725980837ul, 785430967ul,
    849749479ul, 919334987ul, 994618837ul, 1076067617ul, 1164186217ul,
    1259520799ul, 1362662261ul, 1474249943ul, 1594975441ul, 1725587117ul,
    1866894511ul, 2019773507ul, 2185171673ul, 2364114217ul, 2557710269ul,
    2767159799ul, 2993761039ul, 3238918481ul, 3504151727ul, 3791104843ul,
    4101556399ul, 4294967291ul,
    // Sentinel, so we don‘t have to test the result of lower_bound,
    // or, on 64-bit machines, rest of the table.
#if __SIZEOF_LONG__ != 8
    4294967291ul
#else
    6442450933ul, 8589934583ul, 12884901857ul, 17179869143ul,
    25769803693ul, 34359738337ul, 51539607367ul, 68719476731ul,
    103079215087ul, 137438953447ul, 206158430123ul, 274877906899ul,
    412316860387ul, 549755813881ul, 824633720731ul, 1099511627689ul,
    1649267441579ul, 2199023255531ul, 3298534883309ul, 4398046511093ul,
    6597069766607ul, 8796093022151ul, 13194139533241ul, 17592186044399ul,
    26388279066581ul, 35184372088777ul, 52776558133177ul, 70368744177643ul,
    105553116266399ul, 140737488355213ul, 211106232532861ul, 281474976710597ul,
    562949953421231ul, 1125899906842597ul, 2251799813685119ul,
    4503599627370449ul, 9007199254740881ul, 18014398509481951ul,
    36028797018963913ul, 72057594037927931ul, 144115188075855859ul,
    288230376151711717ul, 576460752303423433ul,
    1152921504606846883ul, 2305843009213693951ul,
    4611686018427387847ul, 9223372036854775783ul,
    18446744073709551557ul, 18446744073709551557ul
#endif
  };
} // namespace __detail

 1 #include <ctime>
 2 #include <iostream>
 3 #include <unordered_map>
 4 using namespace std;
 5 const int N = 6e4+3e3;
 6 void insert_numbers(long long x){
 7     clock_t begin = clock();
 8     unordered_map<long long, int> numbers;
 9 
10     for (int i = 1; i <= N; i++)
11         numbers[i * x] = i;
12 
13     long long sum = 0;
14 
15     for (auto &entry : numbers)
16         sum += (entry.first / x) * entry.second;
17 
18     printf("x = %lld: %.3lf seconds, sum = %lld\n", x, (double) (clock() - begin) / CLOCKS_PER_SEC, sum);
19 }
20 
21 int main() {
22     //insert_numbers(107897);
23     insert_numbers(126271);
24 }