Inteprolation and binary search

/*
    Вариант 6.
    Найти заданный целочисленный элемент в не отсортированном массиве.
    Интерполирующий поиск.
*/

#include <iostream>
#include <cstdlib>
#include <vector>
#include <fstream>
#include <algorithm>
#include <iterator>

using namespace std;

int linearSearch( vector<int> v, int searchItem )
{
    cout << "Not sorted array: ";
    copy(v.begin(), v.end(), ostream_iterator<int>(cout, " "));
    cout << endl;

    for (vector<int>::iterator it = v.begin(); it != v.end(); it++)
        if (*it == searchItem)
            return distance(v.begin(), it);
    return -1;
}

int interpolationSearch( vector<int> v, int searchItem )
{
    sort(v.begin(), v.end());
    cout << "Sorted array: ";
    copy(v.begin(), v.end(), ostream_iterator<int>(cout, " "));
    cout << endl;

    int mid, low = 0, high = v.size() - 1;

    while (v[low] < searchItem && v[high] > searchItem)
    {
        mid = low + ((searchItem - v[low]) * (high - low)) / (v[high] - v[low]);

        if (v[mid] < searchItem)
            low = mid + 1;
        else if (v[mid] > searchItem)
            high = mid - 1;
        else
            return mid;
    }

    if (v[low] == searchItem)
        return low;
    else if (v[high] == searchItem)
        return high;
    else
        return -1;
}

int binarySearch(vector<int> v, int searchItem)
{
    sort(v.begin(), v.end());

    int left = 0, right = v.size() - 1, mid;

    while (left < right - 1)
    {
        mid = (left + right) / 2;

        if (v[mid] < searchItem)
            left = mid;
        else
            right = mid;
    }

    return right;
}

int main()
{
    ifstream fileIn("text.txt");
    vector<int> v;
    int temp;
    while (!fileIn.eof())
    {
        fileIn >> temp;
        v.push_back(temp);
    }
    fileIn.close();

    cout << "Input the element that you want to search: ";
    cin >> temp;

    cout << "Position of search element ( " << temp << " ) - Linear search: " << linearSearch(v, temp) << endl << endl;
    cout << "Position of search element ( " << temp << " ) - Interpolation search: " << interpolationSearch(v, temp) << endl << endl;
    cout << "Position of search element ( " << temp << " ) - Binary search: " << binarySearch(v, temp) << endl << endl;

    system("pause");
    return 0;
}