Given two strings s and t, return true if s is a subsequence of t — meaning every character of s appears in t, in the same relative order, though not necessarily contiguously. Searching for each character of s across all of t from scratch works, but it repeats work every scan already did. The two-pointerTwo PointerUsing two indices that move through one or more sequences to avoid redundant re-scanning. technique walks both strings forward together in a single pass: advance the pointer into t on every step, and advance the pointer into s only when the current characters match. Neither pointer ever moves backward, so t is scanned exactly once no matter how the characters line up.