Submission #666567

#TimeUsernameProblemLanguageResultExecution timeMemory
666567si_joRace (IOI11_race)C++14
Compilation error
0 ms0 KiB
#include "race.h" #include <bits/stdc++.h> #include <ext/pb_ds/assoc_container.hpp> #include <ext/pb_ds/tree_policy.hpp> using namespace __gnu_pbds; #define pbds tree<int, null_type,less<int>, rb_tree_tag,tree_order_statistics_node_update> using namespace std; #define ll long long //#define int ll #define pb push_back #define ppb pop_back #define pf push_front #define ppf pop_front #define all(x) (x).begin(), (x).end() #define uniq(v) (v).erase(unique(all(v)), (v).end()) #define sz(x) (int)((x).size()) #define fr first #define sc second #define vi vector<int> #define vvi vector<vi> #define pii pair<int, int> #define rep(i,a,b) for(int i = a; i < b; i++) #define irep(i, a, b) for(int i = a; i > b; i--) #define mem1(a) memset(a, -1, sizeof(a)) #define mem0(a) memset(a, 0, sizeof(a)) #define clz __builtin_clzll //leading zeroes #define ctz __builtin_ctzll //trailing zeroes #define ppc __builtin_popcountll #define nl cout << '\n' const ll INF = 1e18; const int32_t M = 1e9 + 7; const int32_t MM = 998244353; const int MAX = numeric_limits<int>::max(); const int MIN = numeric_limits<int>::min(); // const int N = 0; int N, K, H[200010][2], L[200010]; int n, ans, k; vi s, d, undo; map<pii, int> wt; void getsize(int cur, int par, vector<set<int>>& adj){ s[cur] = 1; for(int a : adj[cur]) if(a != par){ getsize(a, cur, adj); s[cur] += s[a]; } } int centre(int cur, int par, vector<set<int>>& adj, int tot){ for(int a : adj[cur]) if(a != par && s[a] > tot / 2) return centre(a, cur, adj, tot); return cur; } void count(int cur, int par, vector<set<int>>& adj, bool f, int depth, int len){ if(len > k) return; if(f) d[len] = min(d[len], depth); else ans = min(ans, depth + d[k - len]); for(int a : adj[cur]) if(a != par) count(a, cur, adj, f, depth + 1, len + wt[{a, cur}]); } void centroid(int cur, int par, vector<set<int>>& adj){ getsize(cur, par, adj); int c = centre(cur, par, adj, s[cur]); for(int a : adj[c]){ count(a, c, adj, 0, 1, wt[{a, c}]); count(a, c, adj, 1, 1, wt[{a, c}]); } ans = min(ans, d[k]); for(int i : undo) d[i] = 1e9; undo.clear(); for(int a : adj[c]){ adj[a].erase(c); centroid(a, c, adj); } } void best_path(int N, int K, int H[][2], int L[]){ n = N, k = K; s.resize(n + 1); d.assign(k + 1, 1e9); ans = n; vvi h(n - 1, vi(2)); cin >> h; vector<set<int>> adj(n + 1); rep(i, 0, n - 1){ int u = H[i][0] + 1, v = H[i][1] + 1; adj[u].insert(v); adj[v].insert(u); wt[{u, v}] = wt[{v, u}] = L[i]; } centroid(1, 0, adj); cout << (ans == n ? -1 : ans); nl; }

Compilation message (stderr)

race.cpp:81:6: error: ambiguating new declaration of 'void best_path(int, int, int (*)[2], int*)'
   81 | void best_path(int N, int K, int H[][2], int L[]){
      |      ^~~~~~~~~
In file included from race.cpp:1:
race.h:1:5: note: old declaration 'int best_path(int, int, int (*)[2], int*)'
    1 | int best_path(int N, int K, int H[][2], int L[]);
      |     ^~~~~~~~~
race.cpp: In function 'void best_path(int, int, int (*)[2], int*)':
race.cpp:84:27: error: no match for 'operator>>' (operand types are 'std::istream' {aka 'std::basic_istream<char>'} and 'std::vector<std::vector<int> >')
   84 |  vvi h(n - 1, vi(2)); cin >> h;
      |                       ~~~ ^~ ~
      |                       |      |
      |                       |      std::vector<std::vector<int> >
      |                       std::istream {aka std::basic_istream<char>}
In file included from /usr/include/c++/10/sstream:38,
                 from /usr/include/c++/10/complex:45,
                 from /usr/include/c++/10/ccomplex:39,
                 from /usr/include/x86_64-linux-gnu/c++/10/bits/stdc++.h:54,
                 from race.cpp:2:
/usr/include/c++/10/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<char>; std::basic_istream<_CharT, _Traits>::__istream_type = std::basic_istream<char>]'
  120 |       operator>>(__istream_type& (*__pf)(__istream_type&))
      |       ^~~~~~~~
/usr/include/c++/10/istream:120:36: note:   no known conversion for argument 1 from 'std::vector<std::vector<int> >' to 'std::basic_istream<char>::__istream_type& (*)(std::basic_istream<char>::__istream_type&)' {aka 'std::basic_istream<char>& (*)(std::basic_istream<char>&)'}
  120 |       operator>>(__istream_type& (*__pf)(__istream_type&))
      |                  ~~~~~~~~~~~~~~~~~~^~~~~~~~~~~~~~~~~~~~~~
/usr/include/c++/10/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<char>; std::basic_istream<_CharT, _Traits>::__istream_type = std::basic_istream<char>; std::basic_istream<_CharT, _Traits>::__ios_type = std::basic_ios<char>]'
  124 |       operator>>(__ios_type& (*__pf)(__ios_type&))
      |       ^~~~~~~~
/usr/include/c++/10/istream:124:32: note:   no known conversion for argument 1 from 'std::vector<std::vector<int> >' to 'std::basic_istream<char>::__ios_type& (*)(std::basic_istream<char>::__ios_type&)' {aka 'std::basic_ios<char>& (*)(std::basic_ios<char>&)'}
  124 |       operator>>(__ios_type& (*__pf)(__ios_type&))
      |                  ~~~~~~~~~~~~~~^~~~~~~~~~~~~~~~~~
/usr/include/c++/10/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<char>; std::basic_istream<_CharT, _Traits>::__istream_type = std::basic_istream<char>]'
  131 |       operator>>(ios_base& (*__pf)(ios_base&))
      |       ^~~~~~~~
/usr/include/c++/10/istream:131:30: note:   no known conversion for argument 1 from 'std::vector<std::vector<int> >' to 'std::ios_base& (*)(std::ios_base&)'
  131 |       operator>>(ios_base& (*__pf)(ios_base&))
      |                  ~~~~~~~~~~~~^~~~~~~~~~~~~~~~
/usr/include/c++/10/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<char>; std::basic_istream<_CharT, _Traits>::__istream_type = std::basic_istream<char>]'
  168 |       operator>>(bool& __n)
      |       ^~~~~~~~
/usr/include/c++/10/istream:168:24: note:   no known conversion for argument 1 from 'std::vector<std::vector<int> >' to 'bool&'
  168 |       operator>>(bool& __n)
      |                  ~~~~~~^~~
/usr/include/c++/10/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<char>]'
  172 |       operator>>(short& __n);
      |       ^~~~~~~~
/usr/include/c++/10/istream:172:25: note:   no known conversion for argument 1 from 'std::vector<std::vector<int> >' to 'short int&'
  172 |       operator>>(short& __n);
      |                  ~~~~~~~^~~
/usr/include/c++/10/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<char>; std::basic_istream<_CharT, _Traits>::__istream_type = std::basic_istream<char>]'
  175 |       operator>>(unsigned short& __n)
      |       ^~~~~~~~
/usr/include/c++/10/istream:175:34: note:   no known conversion for argument 1 from 'std::vector<std::vector<int> >' to 'short unsigned int&'
  175 |       operator>>(unsigned short& __n)
      |                  ~~~~~~~~~~~~~~~~^~~
/usr/include/c++/10/istream:179:7: note: candidate: 'std::basic_istream<_CharT, _Traits>& std::basic_istream<_CharT, _Traits>::operator>>(int&) [with _CharT = char; _Traits = std::char_traits<char>]'
  179 |       operator>>(int& __n);
      |       ^~~~~~~~
/usr/include/c++/10/istream:179:23: note:   no known conversion for argument 1 from 'std::vector<std::vector<int> >' to 'int&'
  179 |       operator>>(int& __n);
      |                  ~~~~~^~~
/usr/include/c++/10/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<char>; std::basic_istream<_CharT, _Traits>::__istream_type = std::basic_istream<char>]'
  182 |       operator>>(unsigned int& __n)
      |       ^~~~~~~~
/usr/include/c++/10/istream:182:32: note:   no known conversion for argument 1 from 'std::vector<std::vector<int> >' to 'unsigned int&'
  182 |       operator>>(unsigned int& __n)
      |                  ~~~~~~~~~~~~~~^~~
/usr/include/c++/10/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<char>; std::basic_istream<_CharT, _Traits>::__istream_type = std::basic_istream<char>]'
  186 |       operator>>(long& __n)
      |       ^~~~~~~~
/usr/include/c++/10/istream:186:24: note:   no known conversion for argument 1 from 'std::vector<std::vector<int> >' to 'long int&'
  186 |       operator>>(long& __n)
      |                  ~~~~~~^~~
/usr/include/c++/10/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<char>; std::basic_istream<_CharT, _Traits>::__istream_type = std::basic_istream<char>]'
  190 |       operator>>(unsigned long& __n)
      |       ^~~~~~~~
/usr/include/c++/10/istream:190:33: note:   no known conversion for argument 1 from 'std::vector<std::vector<int> >' to 'long unsigned int&'
  190 |       operator>>(unsigned long& __n)
      |                  ~~~~~~~~~~~~~~~^~~
/usr/include/c++/10/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<char>; std::basic_istream<_CharT, _Traits>::__istream_type = std::basic_istream<char>]'
  195 |       operator>>(long long& __n)
      |       ^~~~~~~~
/usr/include/c++/10/istream:195:29: note:   no known conversion for argument 1 from 'std::vector<std::vector<int> >' to 'long long int&'
  195 |       operator>>(long long& __n)
      |                  ~~~~~~~~~~~^~~
/usr/include/c++/10/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<char>; std::basic_istream<_CharT, _Traits>::__istream_type = std::basic_istream<char>]'
  199 |       operator>>(unsigned long long& __n)
      |       ^~~~~~~~
/usr/include/c++/10/istream:199:38: note:   no known conversion for argument 1 from 'std::vector<std::vector<int> >' to 'long long unsigned int&'
  199 |       operator>>(unsigned long long& __n)
      |                  ~~~~~~~~~~~~~~~~~~~~^~~
/usr/include/c++/10/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<char>; std::basic_istream<_CharT, _Traits>::__istream_type = std::basic_istream<char>]'
  214 |       operator>>(float& __f)
      |       ^~~~~~~~
/usr/include/c++/10/istream:214:25: note:   no known conversion for argument 1 from 'std::vector<std::vector<int> >' to 'float&'
  214 |       operator>>(float& __f)
      |                  ~~~~~~~^~~
/usr/include/c++/10/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<char>; std::basic_istream<_CharT, _Traits>::__istream_type = std::basic_istream<char>]'
  218 |       operator>>(double& __f)
      |       ^~~~~~~~
/usr/include/c++/10/istream:218:26: note:   no known conversion for argument 1 from 'std::vector<std::vector<int> >' to 'double&'
  218 |       operator>>(double& __f)
      |                  ~~~~~~~~^~~
/usr/include/c++/10/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<char>; std::basic_istream<_CharT, _Traits>::__istream_type = std::basic_istream<char>]'
  222 |       operator>>(long double& __f)
      |       ^~~~~~~~
/usr/include/c++/10/istream:222:31: note:   no known conversion for argument 1 from 'std::vector<std::vector<int> >' to 'long double&'
  222 |       operator>>(long double& __f)
      |                  ~~~~~~~~~~~~~^~~
/usr/include/c++/10/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<char>; std::basic_istream<_CharT, _Traits>::__istream_type = std::basic_istream<char>]'
  235 |       operator>>(void*& __p)
      |       ^~~~~~~~
/usr/include/c++/10/istream:235:25: note:   no known conversion for argument 1 from 'std::vector<std::vector<int> >' to 'void*&'
  235 |       operator>>(void*& __p)
      |                  ~~~~~~~^~~
/usr/include/c++/10/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<char>; std::basic_istream<_CharT, _Traits>::__streambuf_type = std::basic_streambuf<char>]'
  259 |       operator>>(__streambuf_type* __sb);
      |       ^~~~~~~~
/usr/include/c++/10/istream:259:36: note:   no known conversion for argument 1 from 'std::vector<std::vector<int> >' to 'std::basic_istream<char>::__streambuf_type*' {aka 'std::basic_streambuf<char>*'}
  259 |       operator>>(__streambuf_type* __sb);
      |                  ~~~~~~~~~~~~~~~~~~^~~~
In file included from /usr/include/c++/10/string:56,
                 from /usr/include/c++/10/bits/locale_classes.h:40,
                 from /usr/include/c++/10/bits/ios_base.h:41,
                 from /usr/include/c++/10/ios:42,
                 from /usr/include/c++/10/istream:38,
                 from /usr/include/c++/10/sstream:38,
                 from /usr/include/c++/10/complex:45,
                 from /usr/include/c++/10/ccomplex:39,
                 from /usr/include/x86_64-linux-gnu/c++/10/bits/stdc++.h:54,
                 from race.cpp:2:
/usr/include/c++/10/bits/basic_string.tcc:1476:5: note: candidate: 'template<class _CharT, class _Traits, class _Alloc> std::basic_istream<_CharT, _Traits>& std::operator>>(std::basic_istream<_CharT, _Traits>&, std::__cxx11::basic_string<_CharT, _Traits, _Alloc>&)'
 1476 |     operator>>(basic_istream<_CharT, _Traits>& __in,
      |     ^~~~~~~~
/usr/include/c++/10/bits/basic_string.tcc:1476:5: note:   template argument deduction/substitution failed:
race.cpp:84:30: note:   'std::vector<std::vector<int> >' is not derived from 'std::__cxx11::basic_string<_CharT, _Traits, _Alloc>'
   84 |  vvi h(n - 1, vi(2)); cin >> h;
      |                              ^
In file included from /usr/include/c++/10/istream:991,
                 from /usr/include/c++/10/sstream:38,
                 from /usr/include/c++/10/complex:45,
                 from /usr/include/c++/10/ccomplex:39,
                 from /usr/include/x86_64-linux-gnu/c++/10/bits/stdc++.h:54,
                 from race.cpp:2:
/usr/include/c++/10/bits/istream.tcc:931:5: note: candidate: 'template<class _CharT, class _Traits> std::basic_istream<_CharT, _Traits>& std::operator>>(std::basic_istream<_CharT, _Traits>&, _CharT&)'
  931 |     operator>>(basic_istream<_CharT, _Traits>& __in, _CharT& __c)
      |     ^~~~~~~~
/usr/include/c++/10/bits/istream.tcc:931:5: note:   template argument deduction/substitution failed:
race.cpp:84:30: note:   deduced conflicting types for parameter '_CharT' ('char' and 'std::vector<std::vector<int> >')
   84 |  vvi h(n - 1, vi(2)); cin >> h;
      |                              ^
In file included from /usr/include/c++/10/sstream:38,
                 from /usr/include/c++/10/complex:45,
                 from /usr/include/c++/10/ccomplex:39,
                 from /usr/include/x86_64-linux-gnu/c++/10/bits/stdc++.h:54,
                 from race.cpp:2:
/usr/include/c++/10/istream:756:5: note: candidate: 'template<class _Traits> std::basic_istream<char, _Traits>& std::operator>>(std::basic_istream<char, _Traits>&, unsigned char&)'
  756 |     operator>>(basic_istream<char, _Traits>& __in, unsigned char& __c)
      |     ^~~~~~~~
/usr/include/c++/10/istream:756:5: note:   template argument deduction/substitution failed:
race.cpp:84:30: note:   cannot convert 'h' (type 'std::vector<std::vector<int> >') to type 'unsigned char&'
   84 |  vvi h(n - 1, vi(2)); cin >> h;
      |                              ^
In file included from /usr/include/c++/10/sstream:38,
                 from /usr/include/c++/10/complex:45,
                 from /usr/include/c++/10/ccomplex:39,
                 from /usr/include/x86_64-linux-gnu/c++/10/bits/stdc++.h:54,
                 from race.cpp:2:
/usr/include/c++/10/istream:761:5: note: candidate: 'template<class _Traits> std::basic_istream<char, _Traits>& std::operator>>(std::basic_istream<char, _Traits>&, signed char&)'
  761 |     operator>>(basic_istream<char, _Traits>& __in, signed char& __c)
      |     ^~~~~~~~
/usr/include/c++/10/istream:761:5: note:   template argument deduction/substitution failed:
race.cpp:84:30: note:   cannot convert 'h' (type 'std::vector<std::vector<int> >') to type 'signed char&'
   84 |  vvi h(n - 1, vi(2)); cin >> h;
      |                              ^
In file included from /usr/include/c++/10/istream:991,
                 from /usr/include/c++/10/sstream:38,
                 from /usr/include/c++/10/complex:45,
                 from /usr/include/c++/10/ccomplex:39,
                 from /usr/include/x86_64-linux-gnu/c++/10/bits/stdc++.h:54,
                 from race.cpp:2:
/usr/include/c++/10/bits/istream.tcc:963:5: note: candidate: 'template<class _CharT2, class _Traits2> std::basic_istream<_CharT, _Traits>& std::operator>>(std::basic_istream<_CharT, _Traits>&, _CharT2*)'
  963 |     operator>>(basic_istream<_CharT, _Traits>& __in, _CharT* __s)
      |     ^~~~~~~~
/usr/include/c++/10/bits/istream.tcc:963:5: note:   template argument deduction/substitution failed:
race.cpp:84:30: note:   mismatched types '_CharT2*' and 'std::vector<std::vector<int> >'
   84 |  vvi h(n - 1, vi(2)); cin >> h;
      |                              ^
In file included from /usr/include/c++/10/sstream:38,
                 from /usr/include/c++/10/complex:45,
                 from /usr/include/c++/10/ccomplex:39,
                 from /usr/include/x86_64-linux-gnu/c++/10/bits/stdc++.h:54,
                 from race.cpp:2:
/usr/include/c++/10/istream:803:5: note: candidate: 'template<class _Traits> std::basic_istream<char, _Traits>& std::operator>>(std::basic_istream<char, _Traits>&, unsigned char*)'
  803 |     operator>>(basic_istream<char, _Traits>& __in, unsigned char* __s)
      |     ^~~~~~~~
/usr/include/c++/10/istream:803:5: note:   template argument deduction/substitution failed:
race.cpp:84:30: note:   cannot convert 'h' (type 'std::vector<std::vector<int> >') to type 'unsigned char*'
   84 |  vvi h(n - 1, vi(2)); cin >> h;
      |                              ^
In file included from /usr/include/c++/10/sstream:38,
                 from /usr/include/c++/10/complex:45,
                 from /usr/include/c++/10/ccomplex:39,
                 from /usr/include/x86_64-linux-gnu/c++/10/bits/stdc++.h:54,
                 from race.cpp:2:
/usr/include/c++/10/istream:808:5: note: candidate: 'template<class _Traits> std::basic_istream<char, _Traits>& std::operator>>(std::basic_istream<char, _Traits>&, signed char*)'
  808 |     operator>>(basic_istream<char, _Traits>& __in, signed char* __s)
      |     ^~~~~~~~
/usr/include/c++/10/istream:808:5: note:   template argument deduction/substitution failed:
race.cpp:84:30: note:   cannot convert 'h' (type 'std::vector<std::vector<int> >') to type 'signed char*'
   84 |  vvi h(n - 1, vi(2)); cin >> h;
      |                              ^
In file included from /usr/include/c++/10/sstream:38,
                 from /usr/include/c++/10/complex:45,
                 from /usr/include/c++/10/ccomplex:39,
                 from /usr/include/x86_64-linux-gnu/c++/10/bits/stdc++.h:54,
                 from race.cpp:2:
/usr/include/c++/10/istream:980:5: note: candidate: 'template<class _Istream, class _Tp> typename std::enable_if<std::__and_<std::__not_<std::is_lvalue_reference<_Tp> >, std::__is_convertible_to_basic_istream<_Istream>, std::__is_extractable<typename std::__is_convertible_to_basic_istream<_Tp>::__istream_type, _Tp&&, void> >::value, typename std::__is_convertible_to_basic_istream<_Tp>::__istream_type>::type std::operator>>(_Istream&&, _Tp&&)'
  980 |     operator>>(_Istream&& __is, _Tp&& __x)
      |     ^~~~~~~~
/usr/include/c++/10/istream:980:5: note:   template argument deduction/substitution failed:
/usr/include/c++/10/istream: In substitution of 'template<class _Istream, class _Tp> typename std::enable_if<std::__and_<std::__not_<std::is_lvalue_reference<_Tp> >, std::__is_convertible_to_basic_istream<_Istream>, std::__is_extractable<typename std::__is_convertible_to_basic_istream<_Tp>::__istream_type, _Tp&&, void> >::value, typename std::__is_convertible_to_basic_istream<_Tp>: