Binary Search

Problem Statement - link #

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

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)

Examples #

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.

Constraints #

• 1 ≤ N ≤ 10^5
• 1 ≤ arr[i], K ≤ 10^6

Solutions #

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