Linear search algorithm template implementation

Question

This template class is a linear search algorithm with a simple search function. I have tested it with int and char and it seems to be working fine. I would like pointers on how I can make it more efficient and on my coding technique. I do know that the standard library provides this algorithm, i am just doing it for fun and practice

sLinear.h

//Linear search template
#ifndef SLINEAR_H
#define SLINEAR_H
namespace fm
{
 template <typename T>
 class sLinear
 {
 T *_list;
 T _item;
 int _sizeOfList;
 public:
 sLinear();
 sLinear(T *myArray, T item, int size);
 ~sLinear();
 int findItem();
 };
 //------public methods------
 template <typename T>
 sLinear<T>::sLinear()
 {
 _list = nullptr;
 _sizeOfList = 0;
 }
 template <typename T>
 sLinear<T>::sLinear(T *myArray, T item, int size)
 {
 _list = myArray;
 _item = item;
 _sizeOfList = size;
 }
 template <typename T>
 sLinear<T>::~sLinear()
 {
 _list = nullptr;
 _sizeOfList = 0;
 }
 template <typename T>
 int sLinear<T>::findItem()
 {
 while (_list != nullptr)
 {
 for (int i = 0; i < _sizeOfList; i++)
 {
 if (_list[i] == _item)
 {
 return i + 1;
 }
 }
 return -1;
 }
 }
}
#endif

main.h

#include<iostream>
#include "sLinear.h"
using namespace fm;
int main()
{
 /* Linear search with integer */
 int iList[] = { 1,9,2,6,5,3,7,4,8,0 };
 int size = (sizeof(iList) / sizeof((iList[0])));
 sLinear<int> mySearch(iList, 8, size);
 int k = mySearch.findItem();
 if (k == -1)
 std::cout << "Item not found!" << std::endl;
 else
 std::cout << "Item found:" << k << std::endl;
 return 0;
}

Answer 1

• Returning int is dubious; it unnecessarily narrows the range of possible return values. Consider retuning an iterator.

• The line if (_list[i] == _item) implies that _list must provide an operator[](int), which is very restrictive. A linear search is just like its name implies, linear. It is expected to work on any linear collection, e.g. forward iterator (maybe even on input iterator).

• The class sLinear exposes one public method, and keeps no state. There's no reason to make it a class. A standalone

  template <typename I>
  I findItem(I first, I last, I::value_type value) {
   ....
  }
  

  will do as well.

• while (_list != nullptr) is very strange. _list never changes; why do you want to loop?

  PS: Could you explain a rationale for returning i+1?

• BlooB: Thank you for your help. I am returning i+1 because in arrays index starts from 0, but most people read from 1.
• vnp: @dirty_feri Programmers read from 0. Non-programmers will hardly use your code.
• BlooB: good point, I will implement the change.
• Incomputable: @vnp, it would be great to use std::iterator_traits<I>::value_type, since it will work for pointers as well.
• Incomputable: Also missing typename will cause compilation error :)