The Knuth–Morris–Pratt string searching algorithm (or KMP algorithm) searches for occurrences of a "word" W within a main "text string" T by employing the observation that when a mismatch occurs, the word itself embodies sufficient information to determine where the next match could begin, thus bypassing re-examination of previously matched characters.

• Time: O(|W| + |T|) (much faster comparing to trivial O(|W| * |T|))
• Space: O(|W|)

• Wikipedia
• YouTube