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STL之五：set/multiset用法詳解
集合
Set、multiset都是集合類，差別在與set中不允許有重複元素，multiset中允許有重複元素。
sets和multiset內部以平衡二叉樹實現
1. 常用函數
1) 構造函數和析構函數
set c:創建空集合,不包含任何元素
set c(op):以op為排序準則，產生一個空的set
set c1(c2):複製c2中的元素到c1中
set c(const value_type *first, const value_type* last):複製[first, last)之間元素構成新集合
set c(const value_type *first, const value_type* last,op):以op為排序準則，複製[first, last)之間元素構成新集合。
c.~set()銷毀所有元素，釋放內存
multiset mc:創建空集合,不包含任何元素
multiset mc(op):以op為排序準則，產生一個空的set
multiset c1(c2):複製c2中的元素到c1中
multiset c(const value_type *first, const value_type* last):複製[first, last)之間元素構成新集合
multiset c(const value_type *first, const value_type* last,op):以op為排序準則，複製[first, last)之間元素構成新集合。
c.~set()銷毀所有元素，釋放內存
// constructing sets
#include <iostream>
#include <set>
bool fncomp (int lhs, int rhs) {return lhs<rhs;}
struct classcomp {
bool operator() (const int& lhs, const int& rhs) const
{return lhs<rhs;}
};
int main ()
{
std::set<int> first; // empty set of ints
int myints[]= {10,20,30,40,50};
std::set<int> second (myints,myints+5); // range
std::set<int> third (second); // a copy of second
std::set<int> fourth (second.begin(), second.end()); // iterator ctor.
std::set<int,classcomp> fifth; // class as Compare
bool(*fn_pt)(int,int) = fncomp;
std::set<int,bool(*)(int,int)> sixth (fn_pt); // function pointer as Compare
return 0;
}
2) 大小、判斷空函數
int size() const:返回容器元素個數
bool empty() const:判斷容器是否為空，若返回true，表明容器已空
3) 增加、刪除函數
pair<iterator,bool> insert( x):插入元素x
iterator insert(iterator it,x):在迭代器it處插入元素x
void insert(const value_type *first,const value_type *last):插入[first, last)之間元素
iterator erase(iterator it):刪除迭代器指針it處元素
iterator erase(iterator first,iterator last):刪除[first, last)之間元素
size_type erase(const Key& key):刪除元素值等於key的元素
#include <iostream>
#include <set>
int main ()
{
std::set<int> myset;
std::set<int>::iterator it;
std::pair<std::set<int>::iterator,bool> ret;
// set some initial values:
for (int i=1; i<=5; ++i) myset.insert(i*10); // set: 10 20 30 40 50
ret = myset.insert(20); // no new element inserted
if (ret.second==false) it=ret.first; // "it" now points to element 20
myset.insert (it,25); // max efficiency inserting
myset.insert (it,24); // max efficiency inserting
myset.insert (it,26); // no max efficiency inserting
int myints[]= {5,10,15}; // 10 already in set, not inserted
myset.insert (myints,myints+3);
std::cout << "myset contains:";
for (it=myset.begin(); it!=myset.end(); ++it)
std::cout << ' ' << *it;
std::cout << '\n';
return 0;
}
#include <iostream>
#include <set>
int main ()
{
std::set<int> myset;
std::set<int>::iterator it;
// insert some values:
for (int i=1; i<10; i++) myset.insert(i*10); // 10 20 30 40 50 60 70 80 90
it = myset.begin();
++it; // "it" points now to 20
myset.erase (it);
myset.erase (40);
it = myset.find (60);
myset.erase (it, myset.end());
std::cout << "myset contains:";
for (it=myset.begin(); it!=myset.end(); ++it)
std::cout << ' ' << *it;
std::cout << '\n';
return 0;
}
4) 遍曆函數
iterator begin():返回首元素的迭代器指針
iterator end()：返回尾元素的迭代器指針
reverse_iterator rbegin():返回尾元素的逆向迭代器指針
reverse_iterator rend():返回首元素前一個位置的迭代器指針
#include <iostream>
#include <set>
int main ()
{
int myints[] = {75,23,65,42,13};
std::set<int> myset (myints,myints+5);
std::cout << "myset contains:";
for (std::set<int>::iterator it=myset.begin(); it!=myset.end(); ++it)
std::cout << ' ' << *it;
std::cout << '\n';
return 0;
}
5) 操作函數
const_iterator lower_bound(const Key& key):返回容器中大於等於key的迭代器指針
const_iterator upper_bound(const Key& key):返回容器中大於key的迭代器指針
int count(const Key& key) const:返回容器中元素等於key的元素的個數
pair<const_iterator,const_iterator> equal_range(const Key& key) const:返回容器中元素值等於key的迭代指針[first, last)
const_iterator find(const Key& key) const:查找功能，返回元素值等於key的迭代器指針
void swap(set& s):交換集合元素
void swap(multiset& s):交換多集合元素
#include <iostream>
#include <set>
int main ()
{
std::set<int> myset;
std::set<int>::iterator itlow,itup;
for (int i=1; i<10; i++) myset.insert(i*10); // 10 20 30 40 50 60 70 80 90
itlow=myset.lower_bound (30); // ^
itup=myset.upper_bound (60); // ^
myset.erase(itlow,itup); // 10 20 70 80 90
std::cout << "myset contains:";
for (std::set<int>::iterator it=myset.begin(); it!=myset.end(); ++it)
std::cout << ' ' << *it;
std::cout << '\n';
return 0;
}
#include "stdafx.h"
#include <iostream>
#include <set>
using namespace std;
int main ()
{
set<int> myset;
for (int i=1; i<=5; i++) myset.insert(i*10); // myset: 10 20 30 40 50
pair<set<int>::const_iterator,set<int>::const_iterator> ret;
ret = myset.equal_range(30);
cout << "the lower bound points to: " << *ret.first << '\n';
cout << "the upper bound points to: " << *ret.second << '\n';
return 0;
}
#include "stdafx.h"
#include <iostream>
#include <set>
using namespace std;
int main ()
{
int myints[]={12,75,10,32,20,25};
set<int> first (myints,myints+3); // 10,12,75
set<int> second (myints+3,myints+6); // 20,25,32
first.swap(second);
cout << "first contains:";
for (set<int>::iterator it=first.begin(); it!=first.end(); ++it)
cout << ' ' << *it;
cout << '\n';
cout << "second contains:";
for (set<int>::iterator it=second.begin(); it!=second.end(); ++it)
cout << ' ' << *it;
cout << '\n';
return 0;
}
最後更新：2017-04-04 07:03:42