set/multiset用法详解

转载：http://blog.csdn.net/longshengguoji/article/details/8546286

集合

使用set或multiset之前，必须加入头文件<set>

Set、multiset都是集合类，差别在与set中不允许有重复元素，multiset中允许有重复元素。



sets和multiset内部以平衡二叉树实现

1. 常用函数

1) 构造函数和析构函数

set c:创建空集合,不包含任何元素

set c(op):以op为排序准则，产生一个空的set

set c1(c2):复制c2中的元素到c1中

set c(const value_type *first, const value_type* last):复制[first, last)之间元素构成新集合

set c(const value_type *first, const value_type* last,op):以op为排序准则，复制[first, last)之间元素构成新集合。

c.~set()销毁所有元素，释放内存

multiset mc:创建空集合,不包含任何元素

multiset mc(op):以op为排序准则，产生一个空的set

multiset c1(c2):复制c2中的元素到c1中

multiset c(const value_type *first, const value_type* last):复制[first, last)之间元素构成新集合

multiset c(const value_type *first, const value_type* last,op):以op为排序准则，复制[first, last)之间元素构成新集合。

c.~set()销毁所有元素，释放内存

[cpp] view
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// 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、判断空函数

int size() const:返回容器元素个数

bool empty() const:判断容器是否为空，若返回true，表明容器已空

3) 增加、删除函数

pair<iterator,bool> insert( x):插入元素x

iterator insert(iterator it,x):在迭代器it处插入元素x

void insert(const value_type *first,const value_type *last):插入[first, last)之间元素

iterator erase(iterator it):删除迭代器指针it处元素

iterator erase(iterator first,iterator last):删除[first, last)之间元素

size_type erase(const Key& key):删除元素值等于key的元素

[cpp] view
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#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;

}

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#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) 遍历函数

iterator begin():返回首元素的迭代器指针

iterator end()：返回尾元素的迭代器指针

reverse_iterator rbegin():返回尾元素的逆向迭代器指针

reverse_iterator rend():返回首元素前一个位置的迭代器指针

[cpp] view
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#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) 操作函数

const_iterator lower_bound(const Key& key):返回容器中大于等于key的迭代器指针

const_iterator upper_bound(const Key& key):返回容器中大于key的迭代器指针

int count(const Key& key) const:返回容器中元素等于key的元素的个数

pair<const_iterator,const_iterator> equal_range(const Key& key) const:返回容器中元素值等于key的迭代指针[first, last)

const_iterator find(const Key& key) const:查找功能，返回元素值等于key的迭代器指针

void swap(set& s):交换集合元素

void swap(multiset& s):交换多集合元素

[cpp] view
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#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;

}

[cpp] view
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#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;

}

[cpp] view
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#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;

}