Two Pointer Approach


OVERVIEW


The two-pointer technique is an algorithmic approach that uses two indices (pointers) to traverse an array efficiently. It is commonly used for searching, sorting, and optimization problems, reducing time complexity from O(N²) to O(N) in many cases. The pointers either move towards each other or in the same direction based on conditions.

Steps


  • Initialize Pointers: Set up two pointers at suitable positions (start & end or both at the start).
  • If working with a sorted array, adjust pointers based on comparisons.
  • If working with a window-based problem, adjust pointers to expand or shrink the window.
  • Update State: Perform necessary operations (sum, merge, partition, etc.) based on conditions.
  • Stop Condition: The algorithm stops when pointers meet or cross, or when a solution is found.