Minsta palindrom efter byte
Givet en sträng som har några små bokstäver och en specialteckenprick(.). Vi måste byta ut alla punkter med något alfabet på ett sådant sätt att den resulterande strängen blir ett palindrom vid många möjliga ersättningar måste vi välja en palindromsträng som är lexikografiskt minst. Om det inte är möjligt att konvertera sträng till palindrom efter alla möjliga ersättningar, utmatning Ej möjligt.
Exempel:
Input : str = ab..e.c.a Output : abcaeacba The smallest palindrome which can be made after replacement is 'abcaeacba' We replaced first dot with 'c' second dot with 'a' third dot with 'a' and fourth dot with 'b' Input : str = ab..e.c.b Output : Not Possible It is not possible to convert above string into palindrome
Vi kan lösa det här problemet på följande sätt Eftersom den resulterande strängen måste vara palindrom kan vi kontrollera ett par av icke-prickade tecken i att starta sig själv om de inte matchar, då är direkt retur inte möjligt eftersom vi kan placera ett nytt tecken på positionen för prickar bara inte någon annanstans.
Därefter itererar vi över tecken i strängen om det aktuella tecknet är prick så kontrollerar vi dess parade tecken (tecken vid (n – i -1):e positionen) om det tecknet också är prick så kan vi ersätta båda tecknen med 'a' eftersom 'a' är det minsta alfabetet med gemener, vilket garanterar den minsta lexikografiska strängen i slutet och ersätter båda med något annat tecken kommer att resultera i en stor palindikografisk sträng. I andra fall om det parade tecknet inte är en prick måste vi för att göra strängpalindrom ersätta nuvarande tecken med dess parade tecken.
So in short If both 'i' and 'n- i- 1' are dot replace them by ‘a’ If one of them is a dot character replace that by other non-dot character
Ovanstående procedur ger oss lexikografiskt minsta palindromsträng.
Genomförande:
C++ // C++ program to get lexicographically smallest // palindrome string #include using namespace std ; // Utility method to check str is possible palindrome // after ignoring . bool isPossiblePalindrome ( string str ) { int n = str . length (); for ( int i = 0 ; i < n / 2 ; i ++ ) { /* If both left and right character are not dot and they are not equal also then it is not possible to make this string a palindrome */ if ( str [ i ] != '.' && str [ n - i -1 ] != '.' && str [ i ] != str [ n - i -1 ]) return false ; } return true ; } // Returns lexicographically smallest palindrom // string if possible string smallestPalindrome ( string str ) { if ( ! isPossiblePalindrome ( str )) return 'Not Possible' ; int n = str . length (); // loop through character of string for ( int i = 0 ; i < n ; i ++ ) { if ( str [ i ] == '.' ) { // if one of character is dot replace dot // with other character if ( str [ n - i - 1 ] != '.' ) str [ i ] = str [ n - i - 1 ]; // if both character are dot then replace // them with smallest character 'a' else str [ i ] = str [ n - i - 1 ] = 'a' ; } } // return the result return str ; } // Driver code to test above methods int main () { string str = 'ab..e.c.a' ; cout < < smallestPalindrome ( str ) < < endl ; return 0 ; }
Java // Java program to get lexicographically // smallest palindrome string class GFG { // Utility method to check str is // possible palindrome after ignoring static boolean isPossiblePalindrome ( char str [] ) { int n = str . length ; for ( int i = 0 ; i < n / 2 ; i ++ ) { /* If both left and right character are not dot and they are not equal also then it is not possible to make this string a palindrome */ if ( str [ i ] != '.' && str [ n - i - 1 ] != '.' && str [ i ] != str [ n - i - 1 ] ) return false ; } return true ; } // Returns lexicographically smallest // palindrome string if possible static void smallestPalindrome ( char str [] ) { if ( ! isPossiblePalindrome ( str )) System . out . println ( 'Not Possible' ); int n = str . length ; // loop through character of string for ( int i = 0 ; i < n ; i ++ ) { if ( str [ i ] == '.' ) { // if one of character is dot // replace dot with other character if ( str [ n - i - 1 ] != '.' ) str [ i ] = str [ n - i - 1 ] ; // if both character are dot // then replace them with // smallest character 'a' else str [ i ] = str [ n - i - 1 ] = 'a' ; } } // return the result for ( int i = 0 ; i < n ; i ++ ) System . out . print ( str [ i ] + '' ); } // Driver code public static void main ( String [] args ) { String str = 'ab..e.c.a' ; char [] s = str . toCharArray (); smallestPalindrome ( s ); } } // This code is contributed // by ChitraNayal
Python 3 # Python 3 program to get lexicographically # smallest palindrome string # Utility method to check str is # possible palindrome after ignoring def isPossiblePalindrome ( str ): n = len ( str ) for i in range ( n // 2 ): # If both left and right character # are not dot and they are not # equal also then it is not possible # to make this string a palindrome if ( str [ i ] != '.' and str [ n - i - 1 ] != '.' and str [ i ] != str [ n - i - 1 ]): return False return True # Returns lexicographically smallest # palindrome string if possible def smallestPalindrome ( str ): if ( not isPossiblePalindrome ( str )): return 'Not Possible' n = len ( str ) str = list ( str ) # loop through character of string for i in range ( n ): if ( str [ i ] == '.' ): # if one of character is dot # replace dot with other character if ( str [ n - i - 1 ] != '.' ): str [ i ] = str [ n - i - 1 ] # if both character are dot # then replace them with # smallest character 'a' else : str [ i ] = str [ n - i - 1 ] = 'a' # return the result return str # Driver code if __name__ == '__main__' : str = 'ab..e.c.a' print ( '' . join ( smallestPalindrome ( str ))) # This code is contributed by ChitraNayal
C# // C# program to get lexicographically // smallest palindrome string using System ; public class GFG { // Utility method to check str is // possible palindrome after ignoring static bool isPossiblePalindrome ( char [] str ) { int n = str . Length ; for ( int i = 0 ; i < n / 2 ; i ++ ) { /* If both left and right character are not dot and they are not equal also then it is not possible to make this string a palindrome */ if ( str [ i ] != '.' && str [ n - i - 1 ] != '.' && str [ i ] != str [ n - i - 1 ]) return false ; } return true ; } // Returns lexicographically smallest // palindrome string if possible static void smallestPalindrome ( char [] str ) { if ( ! isPossiblePalindrome ( str )) Console . WriteLine ( 'Not Possible' ); int n = str . Length ; // loop through character of string for ( int i = 0 ; i < n ; i ++ ) { if ( str [ i ] == '.' ) { // if one of character is dot // replace dot with other character if ( str [ n - i - 1 ] != '.' ) str [ i ] = str [ n - i - 1 ]; // if both character are dot // then replace them with // smallest character 'a' else str [ i ] = str [ n - i - 1 ] = 'a' ; } } // return the result for ( int i = 0 ; i < n ; i ++ ) Console . Write ( str [ i ] + '' ); } // Driver code public static void Main () { String str = 'ab..e.c.a' ; char [] s = str . ToCharArray (); smallestPalindrome ( s ); } } // This code is contributed by PrinciRaj1992
PHP // PHP program to get lexicographically // smallest palindrome string // Utility method to check str is // possible palindrome after ignoring function isPossiblePalindrome ( $str ) { $n = strlen ( $str ); for ( $i = 0 ; $i < $n / 2 ; $i ++ ) { /* If both left and right character are not dot and they are not equal also then it is not possible to make this string a palindrome */ if ( $str [ $i ] != '.' && $str [ $n - $i - 1 ] != '.' && $str [ $i ] != $str [ $n - $i - 1 ]) return false ; } return true ; } // Returns lexicographically smallest // palindrome string if possible function smallestPalindrome ( $str ) { if ( ! isPossiblePalindrome ( $str )) return 'Not Possible' ; $n = strlen ( $str ); // loop through character of string for ( $i = 0 ; $i < $n ; $i ++ ) { if ( $str [ $i ] == '.' ) { // if one of character is dot // replace dot with other character if ( $str [ $n - $i - 1 ] != '.' ) $str [ $i ] = $str [ $n - $i - 1 ]; // if both character are dot // then replace them with // smallest character 'a' else $str [ $i ] = $str [ $n - $i - 1 ] = 'a' ; } } // return the result return $str ; } // Driver code $str = 'ab..e.c.a' ; echo smallestPalindrome ( $str ); // This code is contributed // by ChitraNayal ?>
JavaScript < script > // Javascript program to get lexicographically // smallest palindrome string // Utility method to check str is // possible palindrome after ignoring function isPossiblePalindrome ( str ) { let n = str . length ; for ( let i = 0 ; i < Math . floor ( n / 2 ); i ++ ) { /* If both left and right character are not dot and they are not equal also then it is not possible to make this string a palindrome */ if ( str [ i ] != '.' && str [ n - i - 1 ] != '.' && str [ i ] != str [ n - i - 1 ]) return false ; } return true ; } // Returns lexicographically smallest // palindrome string if possible function smallestPalindrome ( str ) { if ( ! isPossiblePalindrome ( str )) document . write ( 'Not Possible' ); let n = str . length ; // loop through character of string for ( let i = 0 ; i < n ; i ++ ) { if ( str [ i ] == '.' ) { // if one of character is dot // replace dot with other character if ( str [ n - i - 1 ] != '.' ) str [ i ] = str [ n - i - 1 ]; // if both character are dot // then replace them with // smallest character 'a' else str [ i ] = str [ n - i - 1 ] = 'a' ; } } // return the result for ( let i = 0 ; i < n ; i ++ ) document . write ( str [ i ] + '' ); } // Driver code let str = 'ab..e.c.a' ; let s = str . split ( '' ); smallestPalindrome ( s ); // This code is contributed by rag2127 < /script>
Produktion
abcaeacba
Tidskomplexitet: O(n) där n är strängens längd.
Auxiliary Space-komplexitet: O(1)
