Binary Search.cpp

// Binary Search
// Difficulty: BasicAccuracy: 44.32%Submissions: 486K+Points: 1
// Given a sorted array of size N and an integer K, find the position(0-based indexing) 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 <= 105
// 1 <= arr[i] <= 106
// 1 <= K <= 106

class Solution {
  public:
    int binarysearch(int arr[], int n, int k) {
        // code here
        int low=0;
        int high=n-1;
        while(low<=high){
            int mid=(low+high)/2;
            if(arr[mid]==k){
                return mid;
            }else if(arr[mid]>k){
                high=mid-1;
            }else{
                low=mid+1;
            }
        }
        return -1;
    }
};