binarySearch.cpp

// You have been given a sorted(in ascending order) integer array/list(ARR) of size N and an element X. 
//Write a function to search this element in the given input array/list using 'Binary Search'. 
//Return the index of the element in the input array/list. In case the element is not present in the array/list, 
//then return -1.
// Input format :
// The first line contains an Integer 'N' which denotes the size of the array/list.

// Second line contains 'N' single space separated integers representing the elements in the array/list.

// Third line contains an Integer 't' which denotes the number of test cases or queries to be run. 
//Then the test cases follow..

// All the 't' lines henceforth, will take the value of X to be searched for in the array/list.
// Output Format :
// For each test case, print the index at which X is present, -1 otherwise.

// Output for every test case will be printed in a separate line.
#include <bits/stdc++.h>
using namespace std;

int binarySearch(int *input, int n, int val)
{
    int left = 0;
    int right = n-1;
    while (left <= right)
    {
        int mid;
        mid = (left+right)/2;
        if (input[mid] == val)
        {
            return mid;
        }
        else if (input[mid] < val)
        {
            left = mid + 1;
        }
        else
        {
            right = mid - 1;
        }
        
    }
    
    return -1;
}
int main()
{

	int size;
	cin >> size;
	int *input = new int[size];

	for(int i = 0; i < size; ++i)
	{
		cin >> input[i];
	}
	
	int t;
	cin >> t;

	while (t--)
	{
		int val;
		cin >> val;
		cout << binarySearch(input, size, val) << endl;
	}
	
	delete [] input;
	return 0;
}