For production code, I would look up Boyer-Moore and do that. But if I had to answer off the top of my head, based on my memoires of Boyer-Moore, the pseudo-code would look like: Construct table(char-diff, offset) {offset by which to move test string b4 next text} begin: Compare (needle, haystack): if comparison false, lookup in above table to compute next offset. Compare (needle, haystack[next-offset] if comparison still false AND we have not passed end of haystack, repeat. Test which case: did we pass end, or find needle return 0 if passed end, offset to needle in haystack otherwise.

Small optimization : can store length(haystack) and length(needle) to make it faster :)

function isSubstring (needle, haystack) { for(int i=0; i

Note: the question specifically asks for a solution in *pseudo-code* ...