Algorithm to determine if array contains n…n+m?

Question

I saw this question on Reddit, and there were no positive solutions presented, and I thought it would be a perfect question to ask here. This was in a thread about interview

Answer 1

Here is a solution in O(N) time and O(1) extra space for finding duplicates :-

public static boolean check_range(int arr[],int n,int m) {

        for(int i=0;i=m)
                return(false);
        }

        System.out.println("In range");

        int j=0;
        while(j

Explanation:-

1. Bring number to range (0,m-1) by arr[i] = arr[i] - n if out of range return false.
2. for each i check if arr[arr[i]] is unoccupied that is it has value less than m
3. if so swap(arr[i],arr[arr[i]]) and arr[arr[i]] = arr[arr[i]] + m to signal that it is occupied
4. if arr[j] = j and simply add m and increment j
5. if arr[arr[j]] >=m means it is occupied hence current value is duplicate hence return false.
6. if arr[j] >= m then skip