GFG POTD: Elements in the Range Solution

Problem Statement

Given an array arr[] containing positive elements. A and B are two numbers defining a range. The task is to check if the array contains all elements in the given range.

Example 1:

Input: N = 7, A = 2, B = 5
arr[] =  {1, 4, 5, 2, 7, 8, 3}
Output: Yes
Explanation: It has elements between 
range 2-5 i.e 2,3,4,5

Example 2:

Input: N = 7, A = 2, B = 6
arr[] = {1, 4, 5, 2, 7, 8, 3}
Output: No
Explanation: Array does not contain 6.

Your Task:
This is a function problem. You don’t need to take any input, as it is already accomplished by the driver code. You just need to complete the function check_elements() that takes array arr, integer N, integer A, and integer B  as parameters and returns the boolean True if array elements contain all elements in the given range else boolean False.

Note: If the array contains all elements in the given range then driver code outputs Yes otherwise, it outputs No

Expected Time Complexity: O(N).
Expected Auxiliary Space: O(1).

Constraints:
1 ≤ N ≤ 10⁷

Solution

bool check_elements(int arr[], int n, int A, int B)
	{
		
		if(n<=B-A)
		    return false;
		    
		for(int i=0; i<n; i++){
		    if(abs(arr[i])>=A && abs(arr[i])<=B){
		        int index = abs(arr[i])-A;
		        if(arr[index]>0)
		         arr[index]=arr[index]*-1;
		    }
		}
		
		for(int i=0; i<=B-A; i++){
		    if(arr[i]>0)
		    return false; 
		}
		
		return true;
	}