Sorting for equal_range()

[GulHK]

Hello all

I am using 3 vectors each of which is of type struct "ABC". I am trying to find duplicates in each vector using equal_range() method. In order for equal_range() to work, the vectors must be sorted. The criteria for sorting each vector is different, therefore, I can't write a single sort method inside the struct "ABC". Is there any way to write different methods for sorting, one for each vector?

Many Thanks

[Galik]

Sure: http://cplusplus.com/reference/algorithm/sort/

[GulHK]

Thanks Galik
Could you please modify the program below for me.

// sort algorithm example
#include <iostream>
#include <algorithm>
#include <vector>
using namespace std;

struct mystruct {
string a;
string b;
string c;
string d;
string e;
};

Sort function-1 (does it not have to have some relevance to struct mystruct?)
{
    On basis of variables a, b and c
}

Sort function-2 (does it not have to have some relevance to struct mystruct?)
{
    On basis of variables a, d and e
}

Sort function-3 (does it not have to have some relevance to struct mystruct?)
{
    On basis of variables b, c and d
}

int main () {
  
  vector< mystruct > myvector1;
  vector< mystruct >::iterator it1;

  sort (myvector1.begin(), myvector1.end(),Sort function-1);

  vector< mystruct > myvector2;
  vector< mystruct >::iterator it2;

  sort (myvector2.begin(), myvector2.end(),Sort function-2);

  vector< mystruct > myvector3;
  vector< mystruct >::iterator it3;

  sort (myvector3.begin(), myvector3.end(),Sort function-3);

  return 0;
}

[GulHK]

Is this correct?

struct sort_one
{
         bool operator () (const mystruct& lhs , const mystruct& rhs)
         {
               return lhs.a < rhs.a; /* but there are two more variables for sorting myvector1 i-e b and c.
Could you please tell me how do I sort myvector1 on the basis of all three variables? */
         }
};

// likewise for the rest two vectors
// ...

sort (myvector1.begin(), myvector1.end(), sort_one());

[bluecoder]

struct sort_one
{
         bool operator () (const mystruct& lhs , const mystruct& rhs)
         {
               return lhs.a < rhs.a; /* but there are two more variables for sorting myvector1 i-e b and c.
Could you please tell me how do I sort myvector1 on the basis of all three variables? */
         }
} mysort;

// likewise for the rest two vectors
// ...

sort (myvector1.begin(), myvector1.end(), mysort);

[GulHK]

Thank you bluecoder for simplifying the code by using mysort, but could anyone please help me sorting the vector on three struct variables a,b,c in order for equal_range to work?

[Galik]

Here is an example using just two member variables as sort criteria:

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64

#include <ctime> #include <string> #include <vector> #include <cstdlib> #include <iomanip> #include <iostream> #include <algorithm> struct mystruct { int id; std::string a; std::string b; }; bool sort_by_abc(const mystruct& lhs, const mystruct& rhs) { if(lhs.a == rhs.a) { return lhs.b < rhs.b; } return lhs.a < rhs.a; } int main() { // Initialise random numbers std::srand(std::time(0)); mystruct m; std::vector<mystruct> v; std::vector<mystruct>::iterator i; // Add random strings std::string s = "abc"; for(int i = 0; i < 20; ++i) { m.id = i; std::random_shuffle(s.begin(), s.end()); m.a = s; std::random_shuffle(s.begin(), s.end()); m.b = s; v.push_back(m); } std::cout << "Before the sort:\n"; for(i = v.begin(); i != v.end(); ++i) { std::cout << '\t' << std::setw(2) << i->id << ": "; std::cout << i->a << ", " << i->b << '\n'; } std::sort(v.begin(), v.end(), &sort_by_abc); std::cout << "After the sort:\n"; for(i = v.begin(); i != v.end(); ++i) { std::cout << '\t' << std::setw(2) << i->id << ": "; std::cout << i->a << ", " << i->b << '\n'; } return 0; }

Before the sort: 0: cab, bca 1: bca, cab 2: acb, bac 3: cba, cba 4: acb, abc 5: cba, cab 6: abc, cab 7: cab, acb 8: bac, acb 9: acb, abc 10: bac, cab 11: acb, cba 12: acb, cba 13: acb, cab 14: abc, cab 15: abc, acb 16: cba, bca 17: acb, bca 18: cba, cba 19: bac, bca After the sort: 15: abc, acb 6: abc, cab 14: abc, cab 4: acb, abc 9: acb, abc 2: acb, bac 17: acb, bca 13: acb, cab 11: acb, cba 12: acb, cba 8: bac, acb 19: bac, bca 10: bac, cab 1: bca, cab 7: cab, acb 0: cab, bca 16: cba, bca 5: cba, cab 3: cba, cba 18: cba, cba

[GulHK]

Thanks Galik for writing a whole program :)

How will it help in finding duplicates in a vector of struct?

 // sort algorithm example
#include <iostream>
#include <algorithm>
#include <vector>
using namespace std;

struct mystruct {
string a;
string b;
string c;
string d;
string e;
};

Sort function-1
{
   // On basis of variables a, b and c
}

Sort function-2
{
    // On basis of variables a, d and e
}

Sort function-3
{
    // On basis of variables b, c and d
}

int main () {
  
  vector< mystruct > myvector1;
  mystruct obj1;
  obj1.a = "x";
  obj1.b = "g";
  obj1.c  = "m";
  obj1.d = "q";
  obj1.e = "l";

  sort (myvector1.begin(), myvector1.end(),Sort function-1);
  equal_range(); // find duplicates in myvector1 if value of a, b, c == value of any other a ,b, c found in myvector1

  vector< mystruct > myvector2;
  mystruct obj2;
  obj2.a = "k";
  obj2.b = "q";
  obj2.c  = "w";
  obj2.d = "s";
  obj2.e = "r";
  
  sort (myvector2.begin(), myvector2.end(),Sort function-2);
  equal_range(); // find duplicates in myvector2 if value of a, d, e == value of any other a ,d, e found in myvector2


  vector< mystruct > myvector3;
  mystruct obj3;
  obj3.a = "f";
  obj3.b = "h";
  obj3.c  = "i";
  obj3.d = "j";
  obj3.e = "z";

  sort (myvector3.begin(), myvector3.end(),Sort function-3);
  equal_range(); // find duplicates in myvector3 if value of b, c, d == value of any other b , c, d found in myvector3


  return 0;
}