locate index

It determines the location index of a number k.

Code:

---

#include <iostream>
using namespace std;

int main()
{
        int a[1024], k, x, i, flag;
        unsigned int n;

        cin >> k >> n;

        for ( i = 0; i < n; i++ )
        {
                cin >> x;
                a[i] = x;
        }
        for ( i = 0; i < n; i++ )
        {
                if ( a[i] == k )
                {
                        flag = i;
                        break;
                }
                else
                        flag = -1;
        }
        cout << flag <<endl;
}

---

If I use vector instead of array, is there a function that can do that?

std::find. To convert the iterator you get to an index, you have to subtract v.begin() from it.

How do I use this function can you give me an example?

Code:

---

std::vector<int> v;
fill(v);

std::vector<int>::iterator loc = std::find(v.begin(), v.end(), k);
std::vector<int>::size_type idx = loc == v.end() ? -1 : loc - v.begin();

---

You can find a brief description of how to use std::find, along with two examples, at cppreference.com's entry on std::find. Notice that the second example actually demonstrates using std::find with an array.

If you are using an associative container like std::map, on the other hand, then it would be better to use the find function provided by that container as it would be more efficient.

Nice. Thanks