误差矢量

Question

vector<int> :: iterator itr1; 
cin >> query; 
for(i = 0; i < query ; i++) 
{ 
    cin >> checknum; 
    if (binary_search (v.begin(), v.end(), checknum)) 
    { 
     itr1 = lower_bound(v.begin(), v.end(), checknum); 
     cout << "Yes " << itr1 << endl; 
    } 
    else 
    { 
     itr1 = lower_bound(v.begin(), v.end(), checknum); 
     cout << "No " << itr1 << endl; 
    } 
} 

编译过程中我发现了错误：编译消息

solution.cc: In function 'int main()': 
solution.cc:28:18: error: cannot bind 'std::basic_ostream<char>' lvalue to 'std::basic_ostream<char>&&' 
      cout << "Yes " << itr1 << endl; 
       ^
In file included from /usr/include/c++/4.9/iostream:39:0, 
       from solution.cc:4: 
/usr/include/c++/4.9/ostream:602:5: note: initializing argument 1 of 'std::basic_ostream<_CharT, _Traits>& std::operator<<(std::basic_ostream<_CharT, _Traits>&&, const _Tp&) [with _CharT = char; _Traits = std::char_traits<char>; _Tp = __gnu_cxx::__normal_iterator<int*, std::vector<int> >]' 
    operator<<(basic_ostream<_CharT, _Traits>&& __os, const _Tp& __x) 
    ^
solution.cc:33:18: error: cannot bind 'std::basic_ostream<char>' lvalue to 'std::basic_ostream<char>&&' 
      cout << "No " << itr1 << endl; 
       ^
In file included from /usr/include/c++/4.9/iostream:39:0, 
       from solution.cc:4: 
/usr/include/c++/4.9/ostream:602:5: note: initializing argument 1 of 'std::basic_ostream<_CharT, _Traits>& std::operator<<(std::basic_ostream<_CharT, _Traits>&&, const _Tp&) [with _CharT = char; _Traits = std::char_traits<char>; _Tp = __gnu_cxx::__normal_iterator<int*, std::vector<int> >]' 
    operator<<(basic_ostream<_CharT, _Traits>&& __os, const _Tp& __x) 

Answer 1

std::lower_bound返回std::vector<int>::iterator，您可以使用cout不能打印。

也许你的意思是：

cout << "Yes " << *itr1 << endl; 
cout << "No " << *itr1 << endl; 

Answer 2

迭代器不能被传递到std::cout。

得到适当的位置，我们需要从itr1减去v.begin()， 即：

cout << distance(v.begin(), itr1) << endl; 

Answer 3

如果您想要打印的位置，你应该做这样的事情。

std::vector<int>::iterator low,up; 
low=std::lower_bound (v.begin(), v.end(), 20); 
up= std::upper_bound (v.begin(), v.end(), 20); 

std::cout << "lower_bound at position " << (low- v.begin()) << '\n'; 
std::cout << "upper_bound at position " << (up - v.begin()) << '\n'; 

我希望它有帮助。