this and what i wrote (@reddit)

main.cpp

#include <iostream>

using std::cout; using std::endl;
using std::copy;

template <typename T>
void Swap_Elements(T &a, T &b){
 T temp(a); a = b; b = temp;
}

template <typename T, typename Si_ze>
void Bubble_Sort(T* arrayZ, Si_ze s){
 for(Si_ze i = s; i > 0; i--){
  for(Si_ze kk = 0; kk < s; kk++){
   if(arrayZ[i]>arrayZ[i+1]){
    Swap_Elements(arrayZ[i], arrayZ[i+1]);
   }
  }
 }
}

template <typename T, typename Si_ze>
void Insertion_Sort(T* arrayZ, Si_ze s){
 for(Si_ze i = 1; i < s; i++){
  for(Si_ze kk = i; kk > 0; kk--){
   if(arrayZ[kk]<arrayZ[kk-1]){
    Swap_Elements(arrayZ[kk],arrayZ[kk-1]);
   }else{
    break;
   }
  }
 }
}
template<typename T, typename Si_ze>
void Selection_Sort(T* arrayZ, Si_ze s){
 Si_ze temp;
 for(Si_ze i = 0; i < s; i++){
  temp = i;
  for(Si_ze kk = i; kk < s; kk++){
   if(arrayZ[kk] < arrayZ[temp]){
    temp = kk;
   }
  }
  Swap_Elements(arrayZ[i], arrayZ[temp]);
 }
}
template<typename T, typename Si_ze>
void Merge(T* arrayZ, Si_ze first, Si_ze second){
  int i(0),j(first),k(0);
  T* temp = new T[second];
  while(k<second){
   temp[k++] = (arrayZ[i] < arrayZ[j]) ? arrayZ[i++] : arrayZ[j++];
   if(i == first){
    copy(&(arrayZ[j]),&(arrayZ[second]),&(temp[k]));
    break;
    }
   if(j == second){
    copy(&(arrayZ[i]),&(arrayZ[first]),&(temp[k]));
    break;
    }
  }
  for(int m = 0; m < second; m++){
   arrayZ[m] = temp[m];
  }
  delete temp;
}
template<typename T, typename Si_ze>
void Merge_Sort(T* arrayZ,Si_ze s){
 for(int i = 1; i < s; i *= 2){
  for(int kk = 0; kk < s-1; kk += 2*i){
   int secondEnd = (2*i < s-kk) ? 2*i : s-kk;
   Merge(&(arrayZ[kk]), i ,secondEnd);
  }
 }
}

int main(int argc, char** argv){
 int ARRAY[] = {5,1,2,8,3,4,6};
 for(int i = 0; i < 7; i++){
  cout << ARRAY[i] << " ";
 }
 cout << endl;
 Merge_Sort(ARRAY,7);
 for(int i = 0; i < 7; i++){
  cout << ARRAY[i] << " ";
 }

 return 0;
}