STL-set

简介

set是一种随机存储的关联式容器，其关键词（key）和元素（value）是同一个值。set之中所有元素互不相同。set是通过二叉查找树来实现的。

创建

创建一个空的set

  1: set<int> s0 ;

创建一个带大于比较器的set, 默认是小于比较器less<int>

  1: set<int, greater<int>> s1 ;

用数组初始化一个set

  1: int a[3] = {1, 2, 3} ;

  2: set<int> s2(a, a + 3) ;

用拷贝构造函数初始化set

  1: set<int> s1 ;

  2: set<int> s2(s1) ;

区间初始化

  1: set<int> s1 ;

  2: set<int> s2(s1.begin(), s1.end()) ;

自定义比较函数

以类为比较器

  1: struct classcmp

  2: {

  3:   bool operator()(const int& lhs, const int& rhs)

  4:   {

  5:     return lhs < rhs ;

  6:   }

  7: };

  8: 

  9: int main(void)

 10: {

 11:   set<int, classcmp> s5 ;

 12: 

 13:   system("pause") ;

 14:   return 0 ;

 15: }

以函数指针为比较器

  1: bool fncmp(int lhs, int rhs)

  2: {

  3:   return lhs < rhs ;

  4: }

  5: 

  6: int main(void)

  7: {

  8:   bool(*fn_pt)(int, int) = fncmp ;

  9:   set<int, bool(*)(int, int)> s1(fn_pt) ;

 10: 

 11:   system("pause") ;

 12:   return 0 ;

 13: }

 

遍历

正向遍历

使用while

  1: int a[3] = {1, 2, 3} ;

  2: set<int> s(a, a + 3) ;

  3: 

  4: set<int>::const_iterator itor ;

  5: itor = s.begin() ;

  6: 

  7: while (itor != s.end())

  8: {

  9:   cout << *itor << endl ;

 10:   ++itor ;

 11: }

使用for

  1: int a[3] = {1, 2, 3} ;

  2: set<int> s(a, a + 3) ;

  3: 

  4: set<int>::const_iterator itor ;

  5: for (itor = s.begin(); itor != s.end(); ++itor)

  6: {

  7:   cout << *itor << endl ;

  8: }

 

反向遍历

使用while

  1: int a[3] = {1, 2, 3} ;

  2: set<int> s(a, a + 3) ;

  3: 

  4: set<int>::const_reverse_iterator ritor ;

  5: ritor = s.rbegin() ;

  6: 

  7: while (ritor != s.rend())

  8: {

  9:   cout << *ritor << endl ;

 10:   ++ritor ;

 11: }

使用for

  1: int a[3] = {1, 2, 3} ;

  2: set<int> s(a, a + 3) ;

  3: 

  4: set<int>::const_reverse_iterator ritor ;

  5: for (ritor = s.rbegin(); ritor != s.rend(); ++ritor)

  6: {

  7:   cout << *ritor << endl ;

  8: }

插入

插入单个值

  1: set<int> s ;

  2: s.insert(1) ;

批量插入

插入整个数组

  1: int a[3] = {1, 2, 3} ;

  2: set<int> s ;

  3: s.insert(a, a + 3) ;

插入其他set的值

  1: int a[3] = {1, 2, 3} ;

  2: set<int> s(a, a + 3) ;

  3: 

  4: set<int> s1 ;

  5: s1.insert(s.begin(), s.end()) ;

删除

  1: set<int> s ;

  2: for (int i = 1; i <= 5; ++i)

  3:   s.insert(i) ;

  4: 

  5: set<int>::const_iterator citor ;

  6: citor = s.begin() ;

  7: ++citor ; // citor now point to 2

  8: 

  9: // 删除单个元素

 10: s.erase(citor) ; // erase 2 ; 

 11: 

 12: //批量删除

 13: citor = s.find(3) ; // itor now point to 3

 14: s.erase(citor, s.end()) ; // erase 3, 4, 5

 15: 

 16: //删除所有元素

 17: s.erase(s.begin(), s.end()) ;// erase all elements, same as s.clear()

查找

find

  1: set<int> s ;

  2: for (int i = 1; i <= 5; ++i)

  3:   s.insert(i) ;

  4: 

  5: set<int>::iterator itor ;

  6: itor = s.find(4) ;

  7: if(itor != s.end()) // itor point to s.end() if not found

  8:   cout << "found" ;

  9: else

 10:   cout << "not found" ;

count

  1: set<int> s ;

  2: for (int i = 1; i <= 5; ++i)

  3:   s.insert(i) ;

  4: 

  5: set<int>::iterator itor ;

  6: if(s.count(4) == 1) // return 1 if s contains 4, else 0

  7:   cout << "s contains 4" ;

  8: else

  9:   cout << "s does not contains 4" ;

排序

由于set本身是有序的，所以不提供排序函数。