Binary Search

BinarySearch.cpp

//Binary search

#include<iostream>
#include<algorithm>

using namespace std;

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

int main() {
    int n, key;
    cout<<"How many number do you want: ";
    cin>>n;
    int arr[n];
    cout<<"Enter "<<n<<" numbers:"<<endl;
    for(int i=0;i<n;i++)
        cin>>arr[i];
    sort(arr, arr+n);
    cout<<"Sorted elements are:"<<endl;
    for(int i=0;i<n;i++)
        cout<<arr[i]<<" ";

    cout<<"Enter the searching number: ";
    cin>>key;
    int res = binary_search(arr, n, key);
    if(res==0)
        cout<<"Key not found."<<endl;
    else
        cout<<"Key found at position "<<res<<"."<<endl;
    return 0;
}