checking if given vector contains already elements of pair in c++ - c++

Question

let us suppose have following pairs
0 -1
0 -2
0 -3
1- 2
2 -3
3- 4
2 -4
4- 5
5 -6
i would like to insert those pairs into vector , so that i should have each element only one times , for instance
start with empty vector :
0-1 is inserted
now we are checking 0-2 , there exist 0, but not 2, so 0-2 is inserted, we have
0-1
0-2
now 0-3 , 3 is not in the list, so we can insert
0-1
0-2
0-3
now lets us consider 1-2 , of course we have both of them , so skip, now let us consider 2-3, again we can skip, 3-4 , 3 exist but not 4, so we can insert
3-4 , after inserting of 4 , 4 also exist,so reject 2-4 then comes 4-5 and 5-6, so we have following list
0-1
0-2
0-3
3-4
4-5
5-6
i have following code
#include<iostream>
#include<vector>
#include<set>
#include<algorithm>
using namespace std;
struct edge
{
int a, c;
float weight;//edge a-c has weight
bool operator() (edge x, edge y)
{
x.weight < y.weight;
}
};
int noncyclical_sum(vector<edge>s)
{
int total = 0;
std::vector<std::pair<int, int>> b;
auto m = make_pair(s[0].a, s[0].c);
b.push_back(m);
total = total + s[0].weight;
vector<edge>::iterator it;
for (int i = 1; i < s.size(); i++)
{
auto m = make_pair(s[i].a, s[i].c);
//if (find(b.begin(), b.end(), s[i].a) != b.end() && find(b.begin(), b.end(), s[i].c) != b.end())
if (find(b.begin(), b.end(), m.first) != b.end() && find(b.begin(), b.end(), m.second) != b.end())
{
continue; //both element is in the vector
}
else
{
b.push_back(m);
total = total + s[i].weight;
}
std::vector<std::pair<int, int>>::iterator ii;
for (ii = b.begin(); ii != b.end(); ii++)
cout << ii->first << " " << ii->second;
}
}
int main()
{
return 0;
}
at first time , i have pushed first pair, starting from the second one, i am checking if at the same time both element is in vector, i am rejecting pairs and continue, otherwise i push new pairs and continuing , but i have following error
Severity Code Description Project File Line Suppression State
Error C2678 binary '==': no operator found which takes a left-hand operand of type 'std::pair<int,int>' (or there is no acceptable conversion) kurskal_algorithm c:\program files (x86)\microsoft visual studio\2017\enterprise\vc\tools\msvc\14.10.25017\include\xutility 3161
what is wrong ? thanks in advance

Answer 1

The problem is in this line:
if (find(b.begin(), b.end(), m.first) != b.end() && find(b.begin(), b.end(), m.second) != b.end())
Let's check the arguments of std::find call: b.begin() and b.end() are std::vector<std::pair<int, int>>::iterators while m.first is int.
So, you're trying to find int in the vector of pairs. You can't do that.
Also, all of your functions lack the required return statements.