KMP string matching: find a pattern in O(n+m) using the prefix-function failure links.

KMP matches a pattern in linear time by precomputing a failure function that skips redundant comparisons instead of backtracking the text. The signal is what the prefix function actually stores and why the text pointer never moves backward. Here is the answer.

Updated Aug 2026 · Grounded in real Applied AI Engineer interview loops and written to a senior-engineer editorial bar.