thisfileisthetestofthesinglelinked-listanddoublelinked-listtakecarethateachnodeinthelisthaveakeyid,thenodewithsamekeyidcanonlybeaddedonce,beforeonenodeisadded,theroutinewillcheckiftherehavethenodethathavethesamekeyid,ifthelisthave,routinewilldeleltethepreviousnode,andthen