algorithm - find the first longest ascending or descending sub-sequence in a given unsorted sequence by C++ -

i writing c++ program find , print first longest ascending or descending continuous subsequence vector of integers. example, given vector with

 4, 2, 1, 2, 3, 4, 3, 5, 1, 2, 4, 6, 5 

return 1,2,3,4

my code follows:

but, not know how return first optimal solution. example, above sequence has 1, 2, 4, 6 4 long. but, need return 1,2,3,4.

bool findlong(const vector<int> v) {   if (v.size() <1)     return false;   if (v.size() == 1){     cout << v[0] << endl;     return true;   }   vector::const_iterator itr_left, itr_right;   itr_left = v.begin();   itr_right = v.begin()+1;   bool ascending_flag ;   int counter =0;   if (*itr_right > *(itr_right-1)){     bool ascending_flag = true;     ++ascending_counter;       }    else{     bool ascending_flag = false;     ++descending_counter;   }   int longest = int_min;   vector<int>::iterator longest_left = v.begin(), longest_right =v.begin();    ++itr_right;    while (itr_right != v.end())   {    if (ascending_flag && *itr_right > *(itr_right-1))      ++ascending_counter;      if (!ascending_flag&& *itr_right < *(itr_right-1))           ++descending_counter;            if  (ascending_flag&& *itr_right < *(itr_right-1))    {      if (ascending_counter > longest )      {         longest  = ascending_counter;         longest_left = itr_left;         longest_right = itr_right;     }     itr_left = itr_right;         ascending_counter = 0 ;       ascending_flag = false;   }   if  (ascending_flag && *itr_right > *(itr_right-1))   {     if (descending_counter > longest )     {         longest  = descending_counter;         longest_left = itr_left;         longest_right = itr_right;     }            itr_left = itr_right;           descending_counter = 0 ;     ascending_flag = true;   }   ++itr_right;  }  for_each( longest_left , longest_right, print);  cout << endl; }  void print(int i) {   cout << << " , " ; } 

any comments welcome !

thanks !

you have lot of typo in code: hide initialization of ascending_flag length count seems incorrect.

following should work (as long there aren't 2 neighbours same values).

bool findlong(const vector<int>& v) {     if (v.empty())         return false;     if (v.size() == 1) {         cout << v[0] << endl;         return true;     }     vector<int>::const_iterator itr_left = v.begin();     vector<int>::const_iterator itr_right = v.begin() + 1;     vector<int>::const_iterator longest_left = itr_left;     vector<int>::const_iterator longest_right = itr_right;     bool ascending_flag = (*itr_right > *(itr_right - 1));      (++itr_right; itr_right != v.end(); ++itr_right)     {         if (ascending_flag ^ (*itr_right < *(itr_right - 1)))         {             if (itr_right - itr_left > longest_right - longest_left)             {                 longest_left = itr_left;                 longest_right = itr_right;             }             itr_left = itr_right - 1;             ascending_flag = !ascending_flag;         }     }     for_each(longest_left, longest_right, print);     cout << endl;     return true; }