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  1.  
  2. #include <bits/stdc++.h>
  3. using namespace std;
  4.  
  5. string removeReverse(string s)
  6. {
  7.   int i, n = s.size(), j;
  8.   set<int> h[26];
  9.   for (i = 0; i < n; i++)
  10.   {
  11.     h[s[i] - 'a'].insert(i);
  12.   }
  13.  
  14.   int c = 0;
  15.  
  16.   set<int> del;
  17.   int cnt = 0;
  18.  
  19.   while (1)
  20.   {
  21.     if (c == 0)
  22.     {
  23.       int in = INT_MAX;
  24.       for (i = 0; i < 26; i++)
  25.       {
  26.  
  27.         if (h[i].size() >= 2)
  28.         {
  29.           in = min(in, *(h[i].begin()));
  30.         }
  31.       }
  32.       if (in == INT_MAX)
  33.         break;
  34.       del.insert(in);
  35.       h[s[in] - 'a'].erase(h[s[in] - 'a'].begin());
  36.       c = 1 - c;
  37.       cnt++;
  38.     }
  39.     else
  40.     {
  41.  
  42.       int in = -1;
  43.       for (i = 0; i < 26; i++)
  44.       {
  45.  
  46.         if (h[i].size() >= 2)
  47.         {
  48.           in = max(in, *(h[i].rbegin()));
  49.         }
  50.       }
  51.       if (in == -1)
  52.         break;
  53.  
  54.       del.insert(in);
  55.       auto it1 = h[s[in] - 'a'].end();
  56.       it1--;
  57.       h[s[in] - 'a'].erase(it1);
  58.       c = 1 - c;
  59.       cnt++;
  60.     }
  61.   }
  62.   string ss;
  63.   for (i = 0; i < n; i++)
  64.   {
  65.     if (del.find(i) == del.end())
  66.       ss += s[i];
  67.   }
  68.  
  69.   if (cnt % 2 == 1)
  70.     reverse(ss.begin(), ss.end());
  71.  
  72.   return ss;
  73. }
  74. signed main()
  75. {
  76.  
  77.   string s;
  78.   cin >> s;
  79.   cout << removeReverse(s);
  80. }
  81.  
Success #stdin #stdout 0s 5520KB
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https://ideone.com/v6idUy
language:
C++14 (gcc 8.3)
created:
2 years ago
visibility:
public

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