Find Index Pairs of Matching Elements in Arrays

Scenario

Marketing analytics team needs to find common elements between two sorted arrays of user IDs.

Question

Given two sorted integer arrays without duplicates, return the list of index pairs where the elements match, e.g., arr1=[1,4,5,6,7,9], arr2=[1,2,3,6,9] -> [[0,0],[3,3],[5,4]].

Follow-ups:

Discuss possible edge cases.

If the arrays can contain duplicates (arr1=[1,1,4,5,6,6,6,7,9], arr2=[1,2,3,6,6,9,9]), modify your algorithm to return all valid index pairs.

Hints

Think two-pointer merge approach; handle duplicates with nested loops; analyze O(n+m) time.