java - How to search for a pattern within a String/Char array? -


i need pattern in input given user. , return (start,end)position if found.

eg:-

input = a b c d b c d

pattern = d c a

output = 3,6

the pattern need not occur consecutively.

it can d @ start of input, c @ middle , @ end. - valid scenario.

two things confused about.

  • how take input? array? if yes, string or char array?

  • how pattern?

the format of input not matter here: can take both string , sequence strings. trick deciding on algorithm use solve problem.

in case, greedy strategy work:

  • read 2 strings, s (string) , p (pattern).
  • make 2 indexes - si string, , pi pattern, , set them both zero.
  • search letter p.charat(pi) in s starting @ si. if letter cannot found in substring si end, pattern not exist
  • otherwise, take first occurrence of p.charat(pi) in s, set si index plus one, , advance pi one.
  • if reach end of p, done
  • otherwise, go search step, , continue processing until either find pattern, or exhaust string.
  • if need print indexes sequence, add array of indexes, , fill out go. length of array should equal length of p.

note there may multiple solutions problem. when solution exists, algorithm finds first "lexicographic" set of indexes solve problem.


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