binary search.cpp

/*
///////////////////////////////////////////
//Question/Info

Binary Search
Basic Accuracy: 38.43% Submissions: 75148 Points: 1
Given a sorted array of size N and an integer K, find the position at which K is present in the array using binary search.


Example 1:

Input:
N = 5
arr[] = {1 2 3 4 5}
K = 4
Output: 3
Explanation: 4 appears at index 3.

Example 2:

Input:
N = 5
arr[] = {11 22 33 44 55}
K = 445
Output: -1
Explanation: 445 is not present.

Your Task:
You dont need to read input or print anything. Complete the function binarysearch() which takes arr[], N and K as input parameters and returns the index of K in the array. If K is not present in the array, return -1.


Expected Time Complexity: O(LogN)
Expected Auxiliary Space: O(LogN) if solving recursively and O(1) otherwise.


Constraints:
1 <= N <= 104
1 <= arr[i] <= 104

Company Tags
 Accenture Cognizant Infosys Linkedin Oracle Qualcomm TCS Wipro

author: srj_v
///////////////////////////////////////////
*/

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

// #define int 		   long long int
#define sbit(x) 	   __builtin_popcount(x)
#define pb(x) 		   push_back(x)
#define mp(x,y) 	   make_pair(x,y)
#define eb(x) 		   emplace_back(x)
#define ct(x) 		   cout << x << "\n";
#define ct2(x,y) 	   cout << x << " " << y << "\n";
#define tc(x) 		   cout << x << " ";
#define tc2(x,y) 	   cout << x << " " << y << " ";
#define forn(i,n) 	   for(int i = 0; i < (int)(n); ++i)
#define forx(i,x,n)    for(int i = x; i < (int)(n); ++i)
#define nfor(i,n)      for(int i = n-1; i >= 0; --i)
#define all(v) 		   v.begin(),v.end()
#define fsp(x,y)       fixed << setprecision(y) << x
#define PI 			   3.1415926535897932384626433832795
#define MOD 		   1000000007 // (1e9+7)
#define pii 		   pair<int,int>
#define pis 		   pair<int,string>
#define vi  		   vector<int>
#define vii 		   vector<pii>
#define mii 		   map<int,int>
#define p_q            priority_queue // priority_queue<int> (&) priority_queue< int,vi,greater<int> >
#define _IOS      	   ios_base::sync_with_stdio(0); cin.tie(0); cout.tie(0);

typedef long double ld;
typedef long long int lli;

#pragma GCC optimize("Ofast")

void c_p_c()
{
#ifndef ONLINE_JUDGE
	freopen("input.txt", "r", stdin);
	freopen("output.txt", "w", stdout);
#endif
}


int32_t main() {
///////////
	c_p_c();
///////////
	_IOS
//////////

	// code

	/*
	int t ; cin >> t; while(t--){}
	*/



	class Solution {
	public:
		int binarysearch(int arr[], int n, int k) {
			// code here

			int start = 0 ; int end = n;
			int ans = -1;
			while (start <= end) {
				int mid = (start + end) / 2;

				if (arr[mid] > k) {
					end = mid - 1;
				}

				else if (arr[mid] < k) {
					start  = mid + 1;
				}

				else if (arr[mid] == k) {
					ans = mid;
					break;
				}

			}
			return ans;

		}

	};



// cerr << "time: " << clock() << " ms" << '\n';
	return 0;
}