Given a String pattern as "ABCDFGHK" write a function if input strings like XYZ**CDFGABHK**ERYT or LOPI**KHFGDCBA**YRT  should return the starting index of the pattern and if the intput strings are XYZ**CDFGABBHK**ERYT or LOPI**KHFDBA**YRGCT it should return -1. \n\nDo not use any data structures like dict or set to store all the possible combinations of the pattern string. \nThe interviewer said no to regular expressions too. \n\n\nI was not able to solve the problem without using data structures like Set or dict etc. \n\nPlease help with solution.

Given a String pattern as "ABCDFGHK" write a function if input strings like XYZCDFGABHKERYT or LOPIKHFGDCBAYRT  should return the starting index of the pattern 