Given a sorted and rotated array, find if there is a pair with a given sum - GeeksforGeeks

Given a sorted and rotated array, find if there is a pair with a given sum - GeeksforGeeks
Given an array that is sorted and then rotated around an unknown point. Find if array has a pair with given sum 'x'. It may be assumed that all elements in array are distinct.
The idea is to first find the maximum element in array which is the pivot point also and the element just before maximum is the minimum element. Once we have indexes maximum and minimum elements, we use similar meet in middle algorithm (as discussed here in method 1) to find if there is a pair. The only thing new here is indexes are incremented and decremented in rotational manner using modular arithmetic.

bool pairInSortedRotated(int arr[], int n, int x)

{

    // Find the pivot element

    int i;

    for (i=0; i<n-1; i++)

        if (arr[i] > arr[i+1])

            break;

    int l = (i+1)%n;  // l is now index of minimum element

    int r = i;        // r is now index of maximum element

    // Keep moving either l or r till they meet

    while (l != r)

    {

         // If we find a pair with sum x, we return true

         if (arr[l] + arr[r] == x)

              return true;

         // If current pair sum is less, move to the higher sum

         if (arr[l] + arr[r] < x)

              l = (l + 1)%n;

         else  // Move to the lower sum side

              r = (n + r - 1)%n;

    }

    return false;

}

1) Extend the above solution to work for arrays with duplicates allowed.

2) Extend the above solution to find all pairs.

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