Two-Pointer Technique

The two-pointer technique uses two indices that move through an array in a coordinated way. It's powerful for problems involving pairs, palindromes, or partitioning. Opposite Ends Pattern Start one pointer at the beginning and one at the end. Move them toward each other based on some condition. Two Sum with Sorted Array Same Direction Pattern Both pointers start at the beginning. A "fast" pointer explores while a "slow" pointer marks a position. This pattern applies whenever sorted data lets you make a decision that rules out one side. Palindrome checking, three-sum problems, and container-with-most-water all follow the same logic.