Language: C++

#include <iostream>
#include <cstdio>
#include <string>
#include <algorithm>
#include <cmath>
#include <vector>
#define rep(i, n) for(int i = 0; i < n; i++)
using namespace std;
typedef long long ll;

int main() {
    vector<string> s(110);
    cin >> s;
    
    int ans = 1000;
    for(char c = 'a'; c <= 'z'; c++) {
        
        int t = 0;
        while(1) {

            rep(j, s.size()-1) {
                if(s[j] == c || s[j+1] == c) {
                    s[j] = c;
                }
            }

            s.pop_back();

            if(s.size() == 1) {
                ans = min(ans, t);
                break;
            }

            int k;
            for(k = 0; k <= s.size()-2; k++) {
                if(s[k] != s[k+1]) {
                    break;
                }
            }

            if(k == s.size()-1) {
                ans = min(ans, t);
                break;
            }

            t++;
        }
    }

    cout << ans;

    cout << endl;
    return 0;
}

Compiler output:
a.cc: In function 'int main()':
a.cc:13:9: error: no match for 'operator>>' (operand types are 'std::istream' {aka 'std::basic_istream<char>'} and 'std::vector<std::__cxx11::basic_string<char> >')
   13 |     cin >> s;
      |     ~~~ ^~ ~
      |     |      |
      |     |      std::vector<std::__cxx11::basic_string<char> >
      |     std::istream {aka std::basic_istream<char>}
In file included from /usr/include/c++/14/iostream:42,
                 from a.cc:1:
/usr/include/c++/14/istream:170:7: note: candidate: 'std::basic_istream<_CharT, _Traits>::__istream_type& std::basic_istream<_CharT, _Traits>::operator>>(bool&) [with _CharT = char; _Traits = std::char_traits<char>; __istream_type = std::basic_istream<char>]'
  170 |       operator>>(bool& __n)
      |       ^~~~~~~~
/usr/include/c++/14/istream:170:24: note:   no known conversion for argument 1 from 'std::vector<std::__cxx11::basic_string<char> >' to 'bool&'
  170 |       operator>>(bool& __n)
      |                  ~~~~~~^~~
/usr/include/c++/14/istream:174:7: note: candidate: 'std::basic_istream<_CharT, _Traits>& std::basic_istream<_CharT, _Traits>::operator>>(short int&) [with _CharT = char; _Traits = std::char_traits<char>]'
  174 |       operator>>(short& __n);
      |       ^~~~~~~~
/usr/include/c++/14/istream:174:25: note:   no known conversion for argument 1 from 'std::vector<std::__cxx11::basic_string<char> >' to 'short int&'
  174 |       operator>>(short& __n);
      |                  ~~~~~~~^~~
/usr/include/c++/14/istream:177:7: 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>; __istream_type = std::basic_istream<char>]'
  177 |       operator>>(unsigned short& __n)
      |       ^~~~~~~~
/usr/include/c++/14/istream:177:34: note:   no known conversion for argument 1 from 'std::vector<std::__cxx11::basic_string<char> >' to 'short unsigned int&'
  177 |       operator>>(unsigned short& __n)
      |                  ~~~~~~~~~~~~~~~~^~~
/usr/include/c++/14/istream:181:7: note: candidate: 'std::basic_istream<_CharT, _Traits>& std::basic_istream<_CharT, _Traits>::operator>>(int&) [with _CharT = char; _Traits = std::char_traits<char>]'
  181 |       operator>>(int& __n);
      |       ^~~~~~~~
/usr/include/c++/14/istream:181:23: note:   no known conversion for argument 1 from 'std::vector<std::__cxx11::basic_string<char> >' to 'int&'
  181 |       operator>>(int& __n);
      |                  ~~~~~^~~
/usr/include/c++/14/istream:184:7: 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>; __istream_type = std::basic_istream<char>]'
  184 |       operator>>(unsigned int& __n)
      |       ^~~~~~~~
/usr/include/c++/14/istream:184:32: note:   no known conversion for argument 1 from 'std::vector<std::__cxx11::basic_string<char> >' to 'unsigned int&'
  184 |       operator>>(unsigned int& __n)
      |                  ~~~~~~~~~~~~~~^~~
/usr/include/c++/14/istream:188:7: 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>; __istream_type = std::basic_istream<char>]'
  188 |       operator>>(long& __n)
      |       ^~~~~~~~
/usr/include/c++/14/istream:188:24: note:   no known conversion for argument 1 from 'std::vector<std::__cxx11::basic_string<char> >' to 'long int&'
  188 |       operator>>(long& __n)
      |                  ~~~~~~^~~
/usr/include/c++/14/istream:192:7: 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>; __istream_type = std::basic_istream<char>]'
  192 |       operator>>(unsigned long& __n)
      |       ^~~~~~~~
/usr/include/c++/14/istream:192:33: note:   no known conversion for argument 1 from 'std::vector<std::__cxx11::basic_string<char> >' to 'long unsigned int&'
  192 |       operator>>(unsigned long& __n)
      |                  ~~~~~~~~~~~~~~~^~~
/usr/include/c++/14/istream:199:7: 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>; __istream_type = std::basic_istream<char>]'
  199 |       operator>>(long long& __n)
      |       ^~~~~~~~
/usr/include/c++/14/istream:199:29: note:   no known conversion for argument 1 from 'std::vector<std::__cxx11::basic_string<char> >' to 'long long int&'
  199 |       operator>>(long long& __n)
      |                  ~~~~~~~~~~~^~~
/usr/include/c++/14/istream:203:7: 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>; __istream_type = std::basic_istream<char>]'
  203 |       operator>>(unsigned long long& __n)
      |       ^~~~~~~~
/usr/include/c++/14/istream:203:38: note:   no known conversion for argument 1 from 'std::vector<std::__cxx11::basic_string<char> >' to 'long long unsigned int&'
  203 |       operator>>(unsigned long long& __n)
      |                  ~~~~~~~~~~~~~~~~~~~~^~~
/usr/include/c++/14/istream:219:7: note: candidate: 'std::basic_istream<_CharT, _Traits>::__istream_type& std::basic_istream<_CharT, _Traits>::operator>>(float&) [with _CharT = char; _Traits = std::char_traits<char>; __istream_type = std::basic_istream<char>]'
  219 |       operator>>(float& __f)
      |       ^~~~~~~~
/usr/include/c++/14/istream:219:25: note:   no known conversion for argument 1 from 'std::vector<std::__cxx11::basic_string<char> >' to 'float&'
  219 |       operator>>(float& __f)
      |                  ~~~~~~~^~~
/usr/include/c++/14/istream:223:7: note: candidate: 'std::basic_istream<_CharT, _Traits>::__istream_type& std::basic_istream<_CharT, _Traits>::operator>>(double&) [with _CharT = char; _Traits = std::char_traits<char>; __istream_type = std::basic_istream<char>]'
  223 |       operator>>(double& __f)
      |       ^~~~~~~~
/usr/include/c++/14/istream:223:26: note:   no known conversion for argument 1 from 'std::vector<std::__cxx11::basic_string<char> >' to 'double&'
  223 |       operator>>(double& __f)
      |                  ~~~~~~~~^~~
/usr/include/c++/14/istream:227:7: 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>; __istream_type = std::basic_istream<char>]'
  227 |       operator>>(long double& __f)
      |       ^~~~~~~~
/usr/include/c++/14/istream:227:31: note:   no known conversion for argument 1 from 'std::vector<std::__cxx11::basic_string<char> >' to 'long double&'
  227 |       operator>>(long double& __f)
      |                  ~~~~~~~~~~~~~^~~
/usr/include/c++/14/istream:328:7: note: candidate: 'std::basic_istream<_CharT, _Traits>::__istream_type& std::basic_istream<_CharT, _Traits>::operator>>(void*&) [with _CharT = char; _Traits = std::char_traits<char>; __istream_type = std::basic_istream<char>]'
  328 |       operator>>(void*& __p)
      |       ^~~~~~~~
/usr/include/c++/14/istream:328:25: note:   no known conversion for argument 1 from 'std::vector<std::__cxx11::basic_string<char> >' to 'void*&'
  328 |       operator>>(void*& __p)
      |                  ~~~~~~~^~~
/usr/include/c++/14/istream:122:7: note: candidate: 'std::basic_istream<_CharT, _Traits>::__istream_type& std::basic_istream<_CharT, _Traits>::operator>>(__istream_type& (*)(__istream_type&)) [with _CharT = char; _Traits = std::char_traits<char>; __istream_type = std::basic_istream<char>]'
  122 |       operator>>(__istream_type& (*__pf)(__istream_type&))
      |       ^~~~~~~~
/usr/include/c++/14/istream:122:36: note:   no known conversion for argument 1 from 'std::vector<std::__cxx11::basic_string<char> >' to 'std::basic_istream<char>::__istream_type& (*)(std::basic_istream<char>::__istream_type&)' {aka 'std::basic_istream<char>& (*)(std::basic_istream<char>&)'}
  122 |       operator>>(__istream_type& (*__pf)(__istream_type&))
      |                  ~~~~~~~~~~~~~~~~~~^~~~~~~~~~~~~~~~~~~~~~
/usr/include/c++/14/istream:126:7: note: candidate: 'std::basic_istream<_CharT, _Traits>::__istream_type& std::basic_istream<_CharT, _Traits>::operator>>(__ios_type& (*)(__ios_type&)) [with _CharT = char; _Traits = std::char_traits<char>; __istream_type = std::basic_istream<char>; __ios_type = std::basic_ios<char>]'
  126 |       operator>>(__ios_type& (*__pf)(__ios_type&))
      |       ^~~~~~~~
/usr/include/c++/14/istream:126:32: note:   no known conversion for argument 1 from 'std::vector<std::__cxx11::basic_string<char> >' to 'std::basic_istream<char>::__ios_type& (*)(std::basic_istream<char>::__ios_type&)' {aka 'std::basic_ios<char>& (*)(std::basic_ios<char>&)'}
  126 |       operator>>(__ios_type& (*__pf)(__ios_type&))
      |                  ~~~~~~~~~~~~~~^~~~~~~~~~~~~~~~~~
/usr/include/c++/14/istream:133:7: 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>; __istream_type = std::basic_istream<char>]'
  133 |       operator>>(ios_base& (*__pf)(ios_base&))
      |       ^~~~~~~~
/usr/include/c++/14/istream:133:30: note:   no known conversion for argument 1 from 'std::vector<std::__cxx11::basic_string<char> >' to 'std::ios_base& (*)(std::ios_base&)'
  133 |       operator>>(ios_base& (*__pf)(ios_base&))
      |                  ~~~~~~~~~~~~^~~~~~~~~~~~~~~~
/usr/include/c++/14/istream:352:7: note: candidate: 'std::basic_istream<_CharT, _Traits>& std::basic_istream<_CharT, _Traits>::operator>>(__streambuf_type*) [with _CharT = char; _Traits = std::char_traits<char>; __streambuf_type = std::basic_streambuf<char>]'
  352 |       operator>>(__streambuf_type* __sb);
      |       ^~~~~~~~
/usr/include/c++/14/istream:352