c++ vector with max N equal elements' positions -

can positions of max n elements (the equal max elements) using predefined function in stl?

a solution thought of is:

vector<int> maxn(vector<int> original){     vector<int> result;     auto pt = max_element(original.begin(),original.end());     int max = *pt;     while(*pt == max){         result.push_back(distance(original.begin(),pt));         *pt = 0;//assumed elements in original greater 0         pt = max_element(original.begin(),original.end());     }      return result; } 

there must more elegant way this.

once have found max element, make linear pass on vector find matching elements. setting 0 not needed when doing way. original vector being passed value, setting 0 not being seen caller. makes clear implementation:

vector<int> maxn(vector<int> original){     vector<int> result;     if (original.empty()) return result;     const int max = *(max_element(original.begin(), original.end()));     (int = 0; < original.size(); ++i) {         if (original[i] == max) result.push_back(i);     }     return result; } 

it more importatnt implement clear , maintainable code attempt extract maximal reuse c++ library.

if goal not use explicit loop on passed in original vector, use standard c++ template algorithm, recommend creating helper iterator recover index.

struct indexer {     int i_;     indexer (int = 0) : i_(i) {}     indexer & operator ++ () { ++i_; return *this; }     indexer operator ++ (int) { ++i_; return i_ - 1; }     int operator * () const { return i_; }     bool operator != (indexer rhs) const { return i_ != rhs.i_; }     //... whatever else required copy_if }; 

then, can invoke copy_if simple lambda , insert iterator:

copy_if(indexer(), indexer(original.size()), back_inserter(result),         [&](int i) -> bool { return original[i] == max; }); 

however, more obscure straightforward loop presented above.