Run ID 作者 问题 语言 测评结果 Time Memory 代码长度 提交时间
111835 张智博 字符串拼接 C++ Compile Error 0 MS 0 KB 257 2025-03-06 22:27:19

Tests(0/0):

Code:

#include <iostream> #include <string> using namespace std; int main() { string a, b; int n; cin >> a >>endl>> b >>endl>> n; string c = a + b; if (n >= 0 and n < c.size()) { cout << c[n]; } return 0; }

Run Info:

Main.cc: In function 'int main()':
Main.cc:8:14: error: no match for 'operator>>' (operand types are 'std::basic_istream' and '')
     cin >> a >>endl>> b >>endl>> n;
              ^
In file included from /usr/include/c++/5/iostream:40:0,
                 from Main.cc:1:
/usr/include/c++/5/istream:120:7: note: candidate: std::basic_istream<_CharT, _Traits>::__istream_type& std::basic_istream<_CharT, _Traits>::operator>>(std::basic_istream<_CharT, _Traits>::__istream_type& (*)(std::basic_istream<_CharT, _Traits>::__istream_type&)) [with _CharT = char; _Traits = std::char_traits; std::basic_istream<_CharT, _Traits>::__istream_type = std::basic_istream]
       operator>>(__istream_type& (*__pf)(__istream_type&))
       ^
/usr/include/c++/5/istream:120:7: note:   no known conversion for argument 1 from '' to 'std::basic_istream::__istream_type& (*)(std::basic_istream::__istream_type&) {aka std::basic_istream& (*)(std::basic_istream&)}'
/usr/include/c++/5/istream:124:7: note: candidate: std::basic_istream<_CharT, _Traits>::__istream_type& std::basic_istream<_CharT, _Traits>::operator>>(std::basic_istream<_CharT, _Traits>::__ios_type& (*)(std::basic_istream<_CharT, _Traits>::__ios_type&)) [with _CharT = char; _Traits = std::char_traits; std::basic_istream<_CharT, _Traits>::__istream_type = std::basic_istream; std::basic_istream<_CharT, _Traits>::__ios_type = std::basic_ios]
       operator>>(__ios_type& (*__pf)(__ios_type&))
       ^
/usr/include/c++/5/istream:124:7: note:   no known conversion for argument 1 from '' to 'std::basic_istream::__ios_type& (*)(std::basic_istream::__ios_type&) {aka std::basic_ios& (*)(std::basic_ios&)}'
/usr/include/c++/5/istream:131:7: note: candidate: std::basic_istream<_CharT, _Traits>::__istream_type& std::basic_istream<_CharT, _Traits>::operator>>(std::ios_base& (*)(std::ios_base&)) [with _CharT = char; _Traits = std::char_traits; std::basic_istream<_CharT, _Traits>::__istream_type = std::basic_istream]
       operator>>(ios_base& (*__pf)(ios_base&))
       ^
/usr/include/c++/5/istream:131:7: note:   no known conversion for argument 1 from '' to 'std::ios_base& (*)(std::ios_base&)'
/usr/include/c++/5/istream:168:7: note: candidate: std::basic_istream<_CharT, _Traits>::__istream_type& std::basic_istream<_CharT, _Traits>::operator>>(bool&) [with _CharT = char; _Traits = std::char_traits; std::basic_istream<_CharT, _Traits>::__istream_type = std::basic_istream]
       operator>>(bool& __n)
       ^
/usr/include/c++/5/istream:168:7: note:   no known conversion for argument 1 from '' to 'bool&'
/usr/include/c++/5/istream:172:7: note: candidate: std::basic_istream<_CharT, _Traits>& std::basic_istream<_CharT, _Traits>::operator>>(short int&) [with _CharT = char; _Traits = std::char_traits]
       operator>>(short& __n);
       ^
/usr/include/c++/5/istream:172:7: note:   no known conversion for argument 1 from '' to 'short int&'
/usr/include/c++/5/istream:175:7: note: candidate: std::basic_istream<_CharT, _Traits>::__istream_type& std::basic_istream<_CharT, _Traits>::operator>>(short unsigned int&) [with _CharT = char; _Traits = std::char_traits; std::basic_istream<_CharT, _Traits>::__istream_type = std::basic_istream]
       operator>>(unsigned short& __n)
       ^
/usr/include/c++/5/istream:175:7: note:   no known conversion for argument 1 from '' to 'short unsigned int&'
/usr/include/c++/5/istream:179:7: note: candidate: std::basic_istream<_CharT, _Traits>& std::basic_istream<_CharT, _Traits>::operator>>(int&) [with _CharT = char; _Traits = std::char_traits]
       operator>>(int& __n);
       ^
/usr/include/c++/5/istream:179:7: note:   no known conversion for argument 1 from '' to 'int&'
/usr/include/c++/5/istream:182:7: note: candidate: std::basic_istream<_CharT, _Traits>::__istream_type& std::basic_istream<_CharT, _Traits>::operator>>(unsigned int&) [with _CharT = char; _Traits = std::char_traits; std::basic_istream<_CharT, _Traits>::__istream_type = std::basic_istream]
       operator>>(unsigned int& __n)
       ^
/usr/include/c++/5/istream:182:7: note:   no known conversion for argument 1 from '' to 'unsigned int&'
/usr/include/c++/5/istream:186:7: note: candidate: std::basic_istream<_CharT, _Traits>::__istream_type& std::basic_istream<_CharT, _Traits>::operator>>(long int&) [with _CharT = char; _Traits = std::char_traits; std::basic_istream<_CharT, _Traits>::__istream_type = std::basic_istream]
       operator>>(long& __n)
       ^
/usr/include/c++/5/istream:186:7: note:   no known conversion for argument 1 from '' to 'long int&'
/usr/include/c++/5/istream:190:7: note: candidate: std::basic_istream<_CharT, _Traits>::__istream_type& std::basic_istream<_CharT, _Traits>::operator>>(long unsigned int&) [with _CharT = char; _Traits = std::char_traits; std::basic_istream<_CharT, _Traits>::__istream_type = std::basic_istream]
       operator>>(unsigned long& __n)
       ^
/usr/include/c++/5/istream:190:7: note:   no known conversion for argument 1 from '' to 'long unsigned int&'
/usr/include/c++/5/istream:195:7: note: candidate: std::basic_istream<_CharT, _Traits>::__istream_type& std::basic_istream<_CharT, _Traits>::operator>>(long long int&) [with _CharT = char; _Traits = std::char_traits; std::basic_istream<_CharT, _Traits>::__istream_type = std::basic_istream]
       operator>>(long long& __n)
       ^
/usr/include/c++/5/istream:195:7: note:   no known conversion for argument 1 from '' to 'long long int&'
/usr/include/c++/5/istream:199:7: note: candidate: std::basic_istream<_CharT, _Traits>::__istream_type& std::basic_istream<_CharT, _Traits>::operator>>(long long unsigned int&) [with _CharT = char; _Traits = std::char_traits; std::basic_istream<_CharT, _Traits>::__istream_type = std::basic_istream]
       operator>>(unsigned long long& __n)
       ^
/usr/include/c++/5/istream:199:7: note:   no known conversion for argument 1 from '' to 'long long unsigned int&'
/usr/include/c++/5/istream:214:7: note: candidate: std::basic_istream<_CharT, _Traits>::__istream_type& std::basic_istream<_CharT, _Traits>::operator>>(float&) [with _CharT = char; _Traits = std::char_traits; std::basic_istream<_CharT, _Traits>::__istream_type = std::basic_istream]
       operator>>(float& __f)
       ^
/usr/include/c++/5/istream:214:7: note:   no known conversion for argument 1 from '' to 'float&'
/usr/include/c++/5/istream:218:7: note: candidate: std::basic_istream<_CharT, _Traits>::__istream_type& std::basic_istream<_CharT, _Traits>::operator>>(double&) [with _CharT = char; _Traits = std::char_traits; std::basic_istream<_CharT, _Traits>::__istream_type = std::basic_istream]
       operator>>(double& __f)
       ^
/usr/include/c++/5/istream:218:7: note:   no known conversion for argument 1 from '' to 'double&'
/usr/include/c++/5/istream:222:7: note: candidate: std::basic_istream<_CharT, _Traits>::__istream_type& std::basic_istream<_CharT, _Traits>::operator>>(long double&) [with _CharT = char; _Traits = std::char_traits; std::basic_istream<_CharT, _Traits>::__istream_type = std::basic_istream]
       operator>>(long double& __f)
       ^
/usr/include/c++/5/istream:222:7: note:   no known conversion for argument 1 from '' to 'long double&'
/usr/include/c++/5/istream:235:7: note: candidate: std::basic_istream<_CharT, _Traits>::__istream_type& std::basic_istream<_CharT, _Traits>::operator>>(void*&) [with _CharT = char; _Traits = std::char_traits; std::basic_istream<_CharT, _Traits>::__istream_type = std::basic_istream]
       operator>>(void*& __p)
       ^
/usr/include/c++/5/istream:235:7: note:   no known conversion for argument 1 from '' to 'void*&'
/usr/include/c++/5/istream:259:7: note: candidate: std::basic_istream<_CharT, _Traits>& std::basic_istream<_CharT, _Traits>::operator>>(std::basic_istream<_CharT, _Traits>::__streambuf_type*) [with _CharT = char; _Traits = std::char_traits; std::basic_istream<_CharT, _Traits>::__streambuf_type = std::basic_streambuf]
       operator>>(__streambuf_type* __sb);
       ^
/usr/include/c++/5/istream:259:7: note:   no known conversion for argument 1 from '' to 'std::basic_istream::__streambuf_type* {aka std::basic_streambuf*}'
In file included from /usr/include/c++/5/string:53:0,
                 from /usr/include/c++/5/bits/locale_classes.h:40,
                 from /usr/include/c++/5/bits/ios_base.h:41,
                 from /usr/include/c++/5/ios:42,
                 from /usr/include/c++/5/ostream:38,
                 from /usr/include/c++/5/iostream:39,
                 from Main.cc:1:
/usr/include/c++/5/bits/basic_string.tcc:1441:5: note: candidate: template std::basic_istream<_CharT, _Traits>& std::operator>>(std::basic_istream<_CharT, _Traits>&, std::__cxx11::basic_string<_CharT, _Traits, _Alloc>&)
     operator>>(basic_istream<_CharT, _Traits>& __in,
     ^
/usr/include/c++/5/bits/basic_string.tcc:1441:5: note:   template argument deduction/substitution failed:
Main.cc:8:16: note:   couldn't deduce template parameter '_Alloc'
     cin >> a >>endl>> b >>endl>> n;
                ^
In file included from /usr/include/c++/5/iostream:40:0,
                 from Main.cc:1:
/usr/include/c++/5/istream:799:5: note: candidate: std::basic_istream<_CharT2, _Traits2>& std::operator>>(std::basic_istream<_CharT2, _Traits2>&, _CharT2*) [with _CharT2 = char; _Traits2 = std::char_traits; _CharT = char; _Traits = std::char_traits]
     operator>>(basic_istream& __in, char* __s);
     ^
/usr/include/c++/5/istream:799:5: note:   no known conversion for argument 2 from '' to 'char*'
In file included from /usr/include/c++/5/istream:934:0,
                 from /usr/include/c++/5/iostream:40,
                 from Main.cc:1:
/usr/include/c++/5/bits/istream.tcc:923:5: note: candidate: std::basic_istream<_CharT, _Traits>& std::operator>>(std::basic_istream<_CharT, _Traits>&, _CharT&) [with _CharT = char; _Traits = std::char_traits]
     operator>>(basic_istream<_CharT, _Traits>& __in, _CharT& __c)
     ^
/usr/include/c++/5/bits/istream.tcc:923:5: note:   no known conversion for argument 2 from '' to 'char&'
In file included from /usr/include/c++/5/iostream:40:0,
                 from Main.cc:1:
/usr/include/c++/5/istream:756:5: note: candidate: template std::basic_istream& std::operator>>(std::basic_istream&, unsigned char&)
     operator>>(basic_istream& __in, unsigned char& __c)
     ^
/usr/include/c++/5/istream:756:5: note:   template argument deduction/substitution failed:
Main.cc:8:16: note:   cannot convert 'std::endl' (type '') to type 'unsigned char&'
     cin >> a >>endl>> b >>endl>> n;
                ^
In file included from /usr/include/c++/5/iostream:40:0,
                 from Main.cc:1:
/usr/include/c++/5/istream:761:5: note: candidate: template std::basic_istream& std::operator>>(std::basic_istream&, signed char&)
     operator>>(basic_istream& __in, signed char& __c)
     ^
/usr/include/c++/5/istream:761:5: note:   template argument deduction/substitution failed:
Main.cc:8:16: note:   cannot convert 'std::endl' (type '') to type 'signed char&'
     cin >> a >>endl>> b >>endl>> n;
                ^
In file included from /usr/include/c++/5/iostream:40:0,
                 from Main.cc:1:
/usr/include/c++/5/istream:803:5: note: candidate: template std::basic_istream& std::operator>>(std::basic_istream&, unsigned char*)
     operator>>(basic_istream& __in, unsigned char* __s)
     ^
/usr/include/c++/5/istream:803:5: note:   template argument deduction/substitution failed:
Main.cc:8:16: note:   cannot convert 'std::endl' (type '') to type 'unsigned char*'
     cin >> a >>endl>> b >>endl>> n;
                ^
In file included from /usr/include/c++/5/iostream:40:0,
                 from Main.cc:1:
/usr/include/c++/5/istream:808:5: note: candidate: template std::basic_istream& std::operator>>(std::basic_istream&, signed char*)
     operator>>(basic_istream& __in, signed char* __s)
     ^
/usr/include/c++/5/istream:808:5: note:   template argument deduction/substitution failed:
Main.cc:8:16: note:   cannot convert 'std::endl' (type '') to type 'signed char*'
     cin >> a >>endl>> b >>endl>> n;
                ^
In file included from /usr/include/c++/5/iostream:40:0,
                 from Main.cc:1:
/usr/include/c++/5/istream:924:5: note: candidate: template std::basic_istream<_CharT, _Traits>& std::operator>>(std::basic_istream<_CharT, _Traits>&&, _Tp&)
     operator>>(basic_istream<_CharT, _Traits>&& __is, _Tp& __x)
     ^
/usr/include/c++/5/istream:924:5: note:   template argument deduction/substitution failed:
Main.cc:8:16: note:   couldn't deduce template parameter '_Tp'
     cin >> a >>endl>> b >>endl>> n;
                ^
Main.cc:10:22: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
     if (n >= 0 and n < c.size()) 
                      ^