Array function nested loops

Question

I have created an nested array for loop that can compare elements within each other. But I want to create a function that represents the inner loop of my nested function. Unfortuantely, I have been very successful.

Here is my program so far:

#include <iostream>
Using namespace std;

bool matchingelements(const int hand[]);
int helpcomparingArray(const int hand[]);

int main ();

Int array[7] = {2,5,3,2,9,7,8};

if (matchingelement(array)) {
cout << "there are 2 matching numbers in this array" << endl;
}
}

bool matchingelements(const int hand[]){
int Count =0;

for (int a=0; a<7;++a){
for (int b=0; b<7;++b){

if (a==b)
continue;
if (array[a] == array[b])
Count ++;
}
}
if (Count ==2){
return true;
}
else {
return false;
}
}

}

int helpcomparingArray(const int hand[]);

I want to create a function to simplify nesting loop (speifically) the inner loop. But i dont know how.

Answer 1

// solution
// http://melpon.org/wandbox/permlink/djVjx6sonYugX4ih

#include <iostream>
#include <vector>
#include <map>
#include <algorithm>

using namespace std;

bool matchingelements(vector<int> const& vec){
map<int,int> m;
for(auto const& item : vec){
// access via [] creates a default constructed element in this case 0!!!!
m[item]++;
}
for_each(m.begin(),m.end(),[](auto const& pair){ cout << pair.first << " " << pair.second << endl; }); //print the map for debug/understanding purpose
return vec.size() > m.size(); //when the map has less elements than the vector there must be at least 2 matching elements!

//you could itereate over the map and check for pair second.
}

int main (){
vector<int> vec = {2,5,3,2,9,7,8};
if (matchingelements(vec)) {
cout << "there are 2 matching numbers in this array" << endl;
}
}