Question

/**
* Performs an index-based linear search on an indexable object for a given value, by using
* operator[].
*
* @param haystack the object to search. Must support operator[] and size(), e.g. a std::vector.
* @param needle the value for which to search
* @return the first index found via linear search at which the object contains the value, or -1 if
* the object does not contain the value.
*/
template <typename IndexedContainer, typename Value>
int LinearSearch(const IndexedContainer &haystack, const Value &needle)

Answer 1

#include <iostream>
#include <vector>

using namespace std;

/**
* Performs an index-based linear search on an indexable object for a given value, by using
* operator[].
*
* @param haystack the object to search. Must support operator[] and size(), e.g. a std::vector.
* @param needle the value for which to search
* @return the first index found via linear search at which the object contains the value, or -1 if
* the object does not contain the value.
*/
template <typename IndexedContainer, typename Value>
int LinearSearch(const IndexedContainer &haystack, const Value &needle) {
    for(int i = 0; i < haystack.size(); ++i) {
        if(haystack[i] == needle) {
            return i;
        }
    }
    return -1;
}

int main() {
    vector<int> vec;
    vec.push_back(4);
    vec.push_back(2);
    vec.push_back(7);
    vec.push_back(9);
    cout << LinearSearch(vec, 2) << endl;   // prints 1
    cout << LinearSearch(vec, 5) << endl;   // prints -1
    return 0;
}