What is the two pointers pattern and when should you use it?

The two pointers pattern uses two index variables that move through the data structure, typically from opposite ends toward the middle or from the same end at different speeds. Use it on sorted arrays or linked lists when you need to find pairs, compare elements, or partition data. The pattern reduces nested loops from O of n squared to O of n by eliminating redundant comparisons. Recognize it when the input is sorted and the problem asks about pairs summing to a target, removing duplicates in place, merging sorted arrays, or checking palindromes.