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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
     
       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
     

> s1 ;

用数组初始化一个set

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

2: set
     
       s2(a, a + 3) ;
     

用拷贝构造函数初始化set

1: set
     
       s1 ;
     

2: set
     
       s2(s1) ;
     

区间初始化

1: set
     
       s1 ;
     

2: set
     
       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
     
       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
     
       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
     
       s(a, a + 3) ;
     

3:

4: set
     
      ::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
     
       s(a, a + 3) ;
     

3:

4: set
     
      ::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
     
       s(a, a + 3) ;
     

3:

4: set
     
      ::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
     
       s(a, a + 3) ;
     

3:

4: set
     
      ::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
     
       s ;
     

2: s.insert(1) ;

成片插入

插入整个数组

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

2: set
     
       s ;
     

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

插入其他set的值

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

2: set
     
       s(a, a + 3) ;
     

3:

4: set
     
       s1 ;
     

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

删除

1: set
     
       s ;
     

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

3:   s.insert(i) ;

4:

5: set
     
      ::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: //成片删除

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
     
       s ;
     

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

3:   s.insert(i) ;

4:

5: set
     
      ::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
     
       s ;
     

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

3:   s.insert(i) ;

4:

5: set
     
      ::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。