What is the Two Pointers technique?

The Two Pointers technique is an algorithmic pattern that uses two pointers to iterate through a data structure, typically an array or a list, until they meet or satisfy a certain condition. This approach can significantly optimize solutions, often reducing time complexity.

What are the common patterns for the Two Pointers algorithm?

Common patterns include using two pointers that move from opposite ends of an array towards the center (e.g., for finding pairs), and two pointers that move in the same direction but at different speeds (e.g., for detecting cycles in a linked list).

Array & List Manipulation

Two Pointers Algorithm

Master the Two Pointers technique for optimizing solutions to array and list-based problems. This guide covers key patterns and provides AI-powered insights.

Two Sum II - Input Array is Sorted

A classic example of the two-pointers pattern with pointers at opposite ends. Given a sorted array, find two numbers that add up to a specific target.

                            function twoSum(numbers, target) {
                            let left = 0;
                            let right = numbers.length - 1;
                            
                            while (left < right) {
                            let sum = numbers[left] + numbers[right];
                            if (sum === target) {
                            return [left + 1, right + 1];
                            } else if (sum < target) {
                            left++;
                            } else {
                            right--;
                            }
                            }
                            }
                        

AI Coach Hint: The sorted nature of the input array is the key giveaway to use the two-pointers from opposite ends. If the sum is too small, you need a larger number, so you move the left pointer. If the sum is too large, you need a smaller number, so you move the right pointer.