בדוק אם מחרוזת עוקבת אחר סדר התווים שהוגדרו על ידי דפוס או לא | סט 2
בהינתן מחרוזת קלט ודפוס, בדוק אם התווים במחרוזת הקלט עוקבים אחר אותו סדר כפי שנקבע על ידי התווים הקיימים בדפוס. נניח שלא יהיו תווים כפולים בתבנית.
פתרון נוסף לאותה בעיה פורסם כָּאן .
דוגמאות:
Input: string = 'engineers rock' pattern = 'er'; Output: true All 'e' in the input string are before all 'r'. Input: string = 'engineers rock' pattern = 'egr'; Output: false There are two 'e' after 'g' in the input string. Input: string = 'engineers rock' pattern = 'gsr'; Output: false There are one 'r' before 's' in the input string.
הרעיון כאן הוא לצמצם את המחרוזת הנתונה לתבנית הנתונה. עבור תווים שניתנו בתבנית אנו שומרים רק את התווים המתאימים במחרוזת. במחרוזת החדשה אנו מוחקים תווים חוזרים ונשנים. המחרוזת ששונתה צריכה להיות שווה לתבנית שניתנה. לבסוף אנו משווים מחרוזת שונה לתבנית הנתונה ומחזירים נכון לשווא בהתאם.
אִיוּר:
str = 'bfbaeadeacc' pat[] = 'bac' 1) Remove extra characters from str (characters that are not present in pat[] str = 'bbaaacc' [f e and d are removed] 3) Removed consecutive repeating occurrences of characters str = 'bac' 4) Since str is same as pat[] we return true
להלן יישום השלבים לעיל.
// C++ code for the above approach #include #include using namespace std ; bool followsPattern ( string str string pattern ) { // Insert all characters of pattern in a hash set unordered_set < char > patternSet ; for ( int i = 0 ; i < pattern . length (); i ++ ) { patternSet . insert ( pattern [ i ]); } // Build modified string (string with characters only from pattern are taken) string modifiedStr = str ; for ( int i = str . length () - 1 ; i >= 0 ; i -- ) { if ( patternSet . find ( str [ i ]) == patternSet . end ()) { modifiedStr . erase ( i 1 ); } } // Remove more than one consecutive occurrences of pattern characters from modified string for ( int i = modifiedStr . length () - 1 ; i > 0 ; i -- ) { if ( modifiedStr [ i ] == modifiedStr [ i - 1 ]) { modifiedStr . erase ( i 1 ); } } // After above modifications the length of modified string must be same as pattern length if ( pattern . length () != modifiedStr . length ()) { return false ; } // And pattern characters must also be same as modified string characters for ( int i = 0 ; i < pattern . length (); i ++ ) { if ( pattern [ i ] != modifiedStr [ i ]) { return false ; } } return true ; } int main () { string str = 'engineers rock' ; string pattern = 'er' ; cout < < 'Expected: true Actual: ' < < followsPattern ( str pattern ) < < endl ; str = 'engineers rock' ; pattern = 'egr' ; cout < < 'Expected: false Actual: ' < < followsPattern ( str pattern ) < < endl ; str = 'engineers rock' ; pattern = 'gsr' ; cout < < 'Expected: false Actual: ' < < followsPattern ( str pattern ) < < endl ; str = 'engineers rock' ; pattern = 'eger' ; cout < < 'Expected: true Actual: ' < < followsPattern ( str pattern ) < < endl ; return 0 ; } // This code is contributed by adityashatmfh
Java // Java program to check if characters of a string follow // pattern defined by given pattern. import java.util.* ; public class OrderOfCharactersForPattern { public static boolean followsPattern ( String str String pattern ) { // Insert all characters of pattern in a hash set Set < Character > patternSet = neHashSet <> (); for ( int i = 0 ; i < pattern . length (); i ++ ) patternSet . add ( pattern . charAt ( i )); // Build modified string (string with characters only from // pattern are taken) StringBuilder modifiedString = new StringBuilder ( str ); for ( int i = str . length () - 1 ; i >= 0 ; i -- ) if ( ! patternSet . contains ( modifiedString . charAt ( i ))) modifiedString . deleteCharAt ( i ); // Remove more than one consecutive occurrences of pattern // characters from modified string. for ( int i = modifiedString . length () - 1 ; i > 0 ; i -- ) if ( modifiedString . charAt ( i ) == modifiedString . charAt ( i - 1 )) modifiedString . deleteCharAt ( i ); // After above modifications the length of modified string // must be same as pattern length if ( pattern . length () != modifiedString . length ()) return false ; // And pattern characters must also be same as modified string // characters for ( int i = 0 ; i < pattern . length (); i ++ ) if ( pattern . charAt ( i ) != modifiedString . charAt ( i )) return false ; return true ; } // Driver program int main () { String str = 'engineers rock' ; String pattern = 'er' ; System . out . println ( 'Expected: true Actual: ' + followsPattern ( str pattern )); str = 'engineers rock' ; pattern = 'egr' ; System . out . println ( 'Expected: false Actual: ' + followsPattern ( str pattern )); str = 'engineers rock' ; pattern = 'gsr' ; System . out . println ( 'Expected: false Actual: ' + followsPattern ( str pattern )); str = 'engineers rock' ; pattern = 'eger' ; System . out . println ( 'Expected: true Actual: ' + followsPattern ( str pattern )); return 0 ; } }
Python3 # Python3 program to check if characters of # a string follow pattern defined by given pattern. def followsPattern ( string pattern ): # Insert all characters of pattern in a hash set patternSet = set () for i in range ( len ( pattern )): patternSet . add ( pattern [ i ]) # Build modified string (string with characters # only from pattern are taken) modifiedString = string for i in range ( len ( string ) - 1 - 1 - 1 ): if not modifiedString [ i ] in patternSet : modifiedString = modifiedString [: i ] + modifiedString [ i + 1 :] # Remove more than one consecutive occurrences # of pattern characters from modified string. for i in range ( len ( modifiedString ) - 1 0 - 1 ): if modifiedString [ i ] == modifiedString [ i - 1 ]: modifiedString = modifiedString [: i ] + modifiedString [ i + 1 :] # After above modifications the length of # modified string must be same as pattern length if len ( pattern ) != len ( modifiedString ): return False # And pattern characters must also be same # as modified string characters for i in range ( len ( pattern )): if pattern [ i ] != modifiedString [ i ]: return False return True # Driver Code if __name__ == '__main__' : string = 'engineers rock' pattern = 'er' print ( 'Expected: true Actual:' followsPattern ( string pattern )) string = 'engineers rock' pattern = 'egr' print ( 'Expected: false Actual:' followsPattern ( string pattern )) string = 'engineers rock' pattern = 'gsr' print ( 'Expected: false Actual:' followsPattern ( string pattern )) string = 'engineers rock' pattern = 'eger' print ( 'Expected: true Actual:' followsPattern ( string pattern )) # This code is contributed by # sanjeev2552
C# // C# program to check if characters of a string follow // pattern defined by given pattern. using System ; using System.Collections.Generic ; using System.Text ; class GFG { public static bool followsPattern ( String str String pattern ) { // Insert all characters of pattern in a hash set HashSet < char > patternSet = new HashSet < char > (); for ( int i = 0 ; i < pattern . Length ; i ++ ) patternSet . Add ( pattern [ i ]); // Build modified string (string with characters // only from pattern are taken) StringBuilder modifiedString = new StringBuilder ( str ); for ( int i = str . Length - 1 ; i >= 0 ; i -- ) if ( ! patternSet . Contains ( modifiedString [ i ])) modifiedString . Remove ( i 1 ); // Remove more than one consecutive occurrences of pattern // characters from modified string. for ( int i = modifiedString . Length - 1 ; i > 0 ; i -- ) if ( modifiedString [ i ] == modifiedString [ i - 1 ]) modifiedString . Remove ( i 1 ); // After above modifications the length of modified string // must be same as pattern length if ( pattern . Length != modifiedString . Length ) return false ; // And pattern characters must also be same // as modified string characters for ( int i = 0 ; i < pattern . Length ; i ++ ) if ( pattern [ i ] != modifiedString [ i ]) return false ; return true ; } // Driver program public static void Main ( String [] args ) { String str = 'engineers rock' ; String pattern = 'er' ; Console . WriteLine ( 'Expected: true Actual: ' + followsPattern ( str pattern )); str = 'engineers rock' ; pattern = 'egr' ; Console . WriteLine ( 'Expected: false Actual: ' + followsPattern ( str pattern )); str = 'engineers rock' ; pattern = 'gsr' ; Console . WriteLine ( 'Expected: false Actual: ' + followsPattern ( str pattern )); str = 'engineers rock' ; pattern = 'eger' ; Console . WriteLine ( 'Expected: true Actual: ' + followsPattern ( str pattern )); } } // This code is contributed by 29AjayKumar
JavaScript < script > // Javascript program to check if characters of a string follow // pattern defined by given pattern. function followsPattern ( str pattern ) { // Insert all characters of pattern in a hash set let patternSet = new Set (); for ( let i = 0 ; i < pattern . length ; i ++ ) patternSet . add ( pattern [ i ]); // Build modified string (string with characters only from // pattern are taken) let modifiedString = ( str ). split ( '' ); for ( let i = str . length - 1 ; i >= 0 ; i -- ) if ( ! patternSet . has ( modifiedString [ i ])) modifiedString . splice ( i 1 ); // Remove more than one consecutive occurrences of pattern // characters from modified string. for ( let i = modifiedString . length - 1 ; i > 0 ; i -- ) if ( modifiedString [ i ] == modifiedString [ i - 1 ]) modifiedString . splice ( i 1 ); // After above modifications the length of modified string // must be same as pattern length if ( pattern . length != modifiedString . length ) return false ; // And pattern characters must also be same as modified string // characters for ( let i = 0 ; i < pattern . length ; i ++ ) if ( pattern [ i ] != modifiedString [ i ]) return false ; return true ; } // Driver program let str = 'engineers rock' ; let pattern = 'er' ; document . write ( 'Expected: true Actual: ' + followsPattern ( str pattern ) + '
' ); str = 'engineers rock' ; pattern = 'egr' ; document . write ( 'Expected: false Actual: ' + followsPattern ( str pattern ) + '
' ); str = 'engineers rock' ; pattern = 'gsr' ; document . write ( 'Expected: false Actual: ' + followsPattern ( str pattern ) + '
' ); str = 'engineers rock' ; pattern = 'eger' ; document . write ( 'Expected: true Actual: ' + followsPattern ( str pattern ) + '
' ); // This code is contributed by rag2127 < /script>
תְפוּקָה:
Expected: true Actual: true Expected: false Actual: false Expected: false Actual: false Expected: true Actual: true
מורכבות זמן: מורכבות הזמן של ההטמעות לעיל היא למעשה O(mn + n^2) מכיוון שאנו משתמשים ב-deleteCharAt() כדי להסיר תווים. אנו יכולים לייעל את הפתרון הנ"ל לעבודה בזמן ליניארי. במקום להשתמש ב-deleteCharAr() נוכל ליצור מחרוזת ריקה ולהוסיף לה רק תווים נדרשים.
StringBuilder משמש להפעלה על מחרוזת קלט. הסיבה לכך היא ש-StringBuilder ניתן לשינוי ואילו String הוא אובייקט בלתי ניתן לשינוי. כדי ליצור מחרוזת חדשה לוקח רווח O(n) ולכן רווח נוסף הוא O(n).
דנו בשתי גישות נוספות לפתרון בעיה זו.
בדוק אם מחרוזת עוקבת אחר סדר התווים שהוגדרו על ידי דפוס או לא | סט 1
בדוק אם מחרוזת עוקבת אחר סדר התווים שהוגדרו על ידי דפוס או לא | סט 3
