Is Subsequence / visualized

One pointer per string, both starting at index 0, both only ever moving right — so the entire design question is which one advances this step. Here the rule is deliberately lopsided: j walks t on every step, while i walks s only when the two heads agree. Greedy is safe because consuming the earliest occurrence of s[i] can never cost you a later match — it leaves the longest possible tail of t for whatever is left of s. Worth knowing the follow-up, because it changes the answer: if you have many s queries against one fixed t, this scan is the wrong shape. You preprocess t once into a next-occurrence table nxt[pos][c] and then jump through it, answering each query in O(|s|) instead of re-walking all of t.