Binary search

#include <iostream>
#include <string>

using namespace std;

int recursion(int* a, int key, int l, int r) {
    int middle = (l + r) / 2;
    cout << "middle: " << middle << ", left: " << l << ", right: " << r << endl;
    if (a[middle] == key) return middle;
    if (l == middle || r == middle) return -1;
    if (key < a[middle]) return recursion(a, key, l, middle);
    if (key > a[middle]) return recursion(a, key, middle, r);
}

int iterative(int* a, int key, int l, int r) {
    int middle = (l + r) / 2;
    while (true) {
        cout << "middle: " << middle << ", left: " << l << ", right: " << r << endl;
        middle = (l + r) / 2;
        if (key < a[middle]) r = middle - 1;
        else if (key > a[middle]) l = middle + 1;
        else return middle;

        if (l > r) return -1;
    }
}

int main() {
    int a[19] = { 1,2,3,4,5,6,7,8,9,10,11,12,13,14,15,16,17,18,19 };

    cout << "recursion => " << endl;
    cout << recursion(a, 3, 0, 18) << endl;
    cout << "iterative => " << endl;
    cout << iterative(a, 3, 0, 18) << endl;

    system("pause");
}