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Commit 0f72b19

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Upload note code of chapter 5 associated container
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‎5_STL_associated_container/5_7_2_stl_hashtable.h‎

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/*
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* Copyright (c) 1996-1998
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* Silicon Graphics Computer Systems, Inc.
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*
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* Permission to use, copy, modify, distribute and sell this software
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* and its documentation for any purpose is hereby granted without fee,
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* provided that the above copyright notice appear in all copies and
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* that both that copyright notice and this permission notice appear
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* in supporting documentation. Silicon Graphics makes no
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* representations about the suitability of this software for any
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* purpose. It is provided "as is" without express or implied warranty.
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*
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*
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* Copyright (c) 1994
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* Hewlett-Packard Company
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*
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* Permission to use, copy, modify, distribute and sell this software
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* and its documentation for any purpose is hereby granted without fee,
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* provided that the above copyright notice appear in all copies and
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* that both that copyright notice and this permission notice appear
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* in supporting documentation. Hewlett-Packard Company makes no
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* representations about the suitability of this software for any
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* purpose. It is provided "as is" without express or implied warranty.
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*
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*/
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/* NOTE: This is an internal header file, included by other STL headers.
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* You should not attempt to use it directly.
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*/
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#ifndef __SGI_STL_HASH_FUN_H
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#define __SGI_STL_HASH_FUN_H
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#include <stddef.h>
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__STL_BEGIN_NAMESPACE
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// 以下都是用仿函数实现hash function,重载不同数据类型
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template <class _Key> struct hash { };
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// 为字符串进行散列
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inline size_t __stl_hash_string(const char* __s)
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{
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unsigned long __h = 0;
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for ( ; *__s; ++__s)
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__h = 5*__h + *__s; // 采用元素层次相加
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return size_t(__h);
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}
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__STL_TEMPLATE_NULL struct hash<char*>
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{
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size_t operator()(const char* __s) const { return __stl_hash_string(__s); }
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};
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__STL_TEMPLATE_NULL struct hash<const char*>
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{
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size_t operator()(const char* __s) const { return __stl_hash_string(__s); }
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};
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__STL_TEMPLATE_NULL struct hash<char> {
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size_t operator()(char __x) const { return __x; }
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};
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__STL_TEMPLATE_NULL struct hash<unsigned char> {
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size_t operator()(unsigned char __x) const { return __x; }
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};
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__STL_TEMPLATE_NULL struct hash<signed char> {
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size_t operator()(unsigned char __x) const { return __x; }
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};
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__STL_TEMPLATE_NULL struct hash<short> {
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size_t operator()(short __x) const { return __x; }
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};
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__STL_TEMPLATE_NULL struct hash<unsigned short> {
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size_t operator()(unsigned short __x) const { return __x; }
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};
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__STL_TEMPLATE_NULL struct hash<int> {
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size_t operator()(int __x) const { return __x; }
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};
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__STL_TEMPLATE_NULL struct hash<unsigned int> {
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size_t operator()(unsigned int __x) const { return __x; }
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};
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__STL_TEMPLATE_NULL struct hash<long> {
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size_t operator()(long __x) const { return __x; }
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};
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__STL_TEMPLATE_NULL struct hash<unsigned long> {
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size_t operator()(unsigned long __x) const { return __x; }
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};
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__STL_END_NAMESPACE
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#endif /* __SGI_STL_HASH_FUN_H */
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// Local Variables:
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// mode:C++
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// End:
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// file: 5hashtable-test.cpp
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// #include <hash_set> // for hashtable
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#include <backward/hashtable.h> // for hashtable in mingw c++
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#include <iostream>
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using namespace std;
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int main() {
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// hash-table
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// <value, key, hash-func, extract-key, equal-key, allocator>
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// note: hash-table has no default ctor
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__gnu_cxx::hashtable<int,
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int,
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hash<int>,
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_Identity<int>,
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equal_to<int>,
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allocator<int>>
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iht(50, hash<int>(), equal_to<int>()); // 指定50个buckets与函数对象
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cout << iht.size() << endl;
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cout << iht.bucket_count() << endl; // 第一个质数
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cout << iht.max_bucket_count() << endl; // 最后一个质数
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iht.insert_unique(59);
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iht.insert_unique(63);
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iht.insert_unique(108);
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iht.insert_unique(2);
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iht.insert_unique(53);
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iht.insert_unique(55);
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cout << iht.size() << endl;
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// 声明hashtable迭代器
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// __gnu_cxx::hashtable<int,
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// int,
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// hash<int>,
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// _Identity<int>,
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// equal_to<int>,
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// allocator<int>>
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// ::iterator ite = iht.begin();
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// 使用auto可以避免上述长串,注意auto做函数返回类型时不会是引用
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auto ite = iht.begin();
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// 使用迭代器遍历hashtable输出所有节点值
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for (int i = 0; i < iht.size(); ++i, ++ite)
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cout << *ite << ' ';
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cout << endl;
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// 遍历所有buckets,如果节点个数不为0则打印
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for (int i = 0; i < iht.bucket_count(); ++i) {
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int n = iht.elems_in_bucket(i);
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if (n!=0)
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cout << "bucket[" << i << "] has " << n << " elems." << endl;
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}
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// 验证bucket(list)的容量就是buckets vector的大小
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for (int i = 0; i <= 47; ++i) {
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iht.insert_equal(i);
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}
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cout << iht.size() << endl;
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cout << iht.bucket_count() << endl;
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// 遍历所有buckets,如果节点个数不为0则打印
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for (int i = 0; i < iht.bucket_count(); ++i) {
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int n = iht.elems_in_bucket(i);
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if (n!=0)
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cout << "bucket[" << i << "] has " << n << " elems." << endl;
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}
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// 使用迭代器遍历hashtable输出所有节点值
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ite = iht.begin();
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for (int i = 0; i < iht.size(); ++i, ++ite)
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cout << *ite << ' ';
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cout << endl;
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cout << *(iht.find(2)) << endl;
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cout << iht.count(2) << endl;
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// template argument deduction/substitution failed
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// iht.insert_unique(string("jjhou"));
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}
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// file: 5hashset-test.cpp
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#include <iostream>
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#include <hash_set>
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#include <cstring>
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using namespace std;
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// 仿函数
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struct eqstr {
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bool operator() (const char* s1, const char* s2) const {
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return strcmp(s1, s2) == 0;
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}
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};
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void lookup(const __gnu_cxx::hash_set<const char*, hash<const char*>, eqstr>& Set,
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const char* word) {
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__gnu_cxx::hash_set<const char *, hash<const char *>, eqstr>::const_iterator it = Set.find(word);
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cout << " " << word << ": " << (it != Set.end() ? "present" : "not present") << endl;
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}
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int main() {
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__gnu_cxx::hash_set<const char *, hash<const char *>, eqstr> Set;
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Set.insert("kiwi");
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Set.insert("plum");
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Set.insert("apple");
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Set.insert("mango");
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Set.insert("apricot");
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Set.insert("banana");
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lookup(Set, "mango");
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lookup(Set, "apple");
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lookup(Set, "durian");
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auto ite1 = Set.begin();
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auto ite2 = Set.end();
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for (; ite1 != ite2; ++ite1)
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cout << *ite1 << ' ';
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cout << endl;
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__gnu_cxx::hash_set<int> iSet;
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iSet.insert(59);
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iSet.insert(63);
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iSet.insert(108);
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iSet.insert(2);
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iSet.insert(53);
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iSet.insert(55);
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auto ite11 = iSet.begin();
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auto ite22 = iSet.end();
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// 为何已排序:
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// 因为bucket为193(内置28个质数中大于100的最小质数)
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// bucket足够多,造成排序假象
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for (; ite11 != ite22; ++ite11)
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cout << *ite11 << ' ';
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cout << endl;
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iSet.clear();
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iSet.insert(3);
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iSet.insert(196);
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iSet.insert(1);
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iSet.insert(389);
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iSet.insert(194);
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iSet.insert(387);
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ite11 = iSet.begin();
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for (; ite11 != ite22; ++ite11)
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cout << *ite11 << ' ';
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cout << endl;
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}

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