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。