Binary Search

 

#include <bits/stdc++.h>
using namespace std ;

int binary_search(int a[],int n,int key){
    int start{0};
    int end{n-1};
    while (start <= end){
        int mid{(start + end)/2} ;
        if (key == a[mid]){
            return mid ;
        }
        else if (a[mid] > key){
            end = mid - 1 ;
        } else{
            start = mid + 1 ;
        }
    }
    return  -1 ;

}

int main (){
    int n ;
    cin >> n ;
    int a[n];
    for (int i = 0; i < n; ++i) {
        cin >> a[i];

    }
    cout << "enter key " << '\n' ;
    int key ;
    cin >> key ;
    sort(a,a+n) ;
    int position = binary_search(a,n,key) ;
    if (position == -1) cout << "key not found " ;
    else cout << "key found at " << position ;

    return 0 ;
}