C++ set Begin()函数用于返回引用set集合的第一个元素的迭代器。
iterator begin(); //until C++ 11 const_iterator begin() const; //until C++ 11 iterator begin() noexcept; //since C++ 11 const_iterator begin() const noexcept; //since C++ 11
它返回一个指向集合的第一个元素的迭代器。
让我们看一下begin()函数的简单示例:
#include <iostream> #include <set> using namespace std; int main () { set<string> myset= {"Java", "C++", "SQL"}; //show content: cout<<"Contents of myset are: "<<endl; for (set<string>::iterator it=myset.begin(); it!=myset.end(); ++it) cout << *it<< '\n'; return 0; }
输出:
Contents of myset are: C++ Java SQL
在上面的示例中,begin()函数用于返回指向myset集合中第一个元素的迭代器。
让我们看一个简单的例子:
#include <iostream> #include <set> using namespace std; int main() { set<int> c; c.insert(5); c.insert(2); c.insert(4); c.insert(1); c.insert(0); c.insert(9); set<int>::iterator i = c.begin(); while (i != c.end()) cout << *i++ << " "; cout << endl; }
输出:
0 1 2 4 5 9
让我们看一个简单的示例,使用while循环遍历集合:
#include <iostream> #include <set> #include <string> int main() { using namespace std; set<string> myset = { "Nikita","Deep","Priya","Suman","Aman" }; cout<<"Elements of myset are: "<<endl; set<string>::const_iterator it;//declare an iterator it = myset.begin();//assign it to the start of the set while (it != myset.end())//while it hasn't reach the end { cout << *it << "\n"; // print the value of the element it points to ++it;//and iterate to the next element } cout << endl; }
输出:
Elements of myset are: Aman Deep Nikita Priya Suman
在上面的代码中,begin()函数用于返回指向myset集合中第一个元素的迭代器。
让我们看一个简单的例子:
#include <set> #include <iostream> int main( ) { using namespace std; set <int> s1; set <int>::iterator s1_Iter; s1.insert( 1 ); s1.insert( 2 ); s1.insert( 3 ); s1_Iter = s1.begin( ); cout << "The first element of s1 is " << *s1_Iter << endl; s1_Iter = s1.begin( ); s1.erase( s1_Iter ); s1_Iter = s1.begin( ); cout << "The first element of s1 is now " << *s1_Iter << endl; }
输出:
The first element of s1 is 1 The first element of s1 is now 2
在上面的示例中,begin()函数用于返回指向myset集合中第一个元素的迭代器。
祝学习愉快!(内容编辑有误?请选中要编辑内容 -> 右键 -> 修改 -> 提交!)