answersLogoWhite

0

How about a Perl compatible regular expression for grep? I guess that's an algorithm.

This one will search for seven-letter palindromes:

grep -P '(?=^.{7}$)(.)(.)(.).\3\2\1' /path/to/your/dictionary

The -P flag let's grep recognize perl compatible regular expressions (PCRE).

The (?=^.{7}$) looks ahead to make sure it's matching a seven-letter word.

The \1 is a backreference to the first (.) which matches any character. But now it has to match it again, except we're asking it to match in reverse order, \3\2\1 instead of \1\2\3.

Then we have a single dot for the fourth letter, which will match any character.

Just add or subtract subexpressions "(.)" as needed, along with the appropriate number backreferences "/1" to find palindromes.

This is the output from grepping the TWL (the Scrabble dictionary):

deified

halalah

reifier

repaper

reviver

rotator

sememes

User Avatar

Wiki User

12y ago

What else can I help you with?

Related Questions

What is the palindrome of 14?

There is no palindrome for 14.


Write an algorithm to check whether a given string is palindrome or not?

#include <stdio.h> #include <conio.h> #include <string.h> void input(char a[ ]) { int i; printf("\n enter string\n"); scanf("%s",a); } void output(char a[ ]) { printf("\n string is %s",a); } int palindrome(char a[ ]) { int n,i; n=count(a); n=n-1; i=0; for(;a[n]==a[i] && n>=i;i++,n--); if(n>=i) return 0; else return 1; } void main( ) { char a[80],b[80],s; int n; printf("\n check palindrome"); input(a); n=palindrome(a); output(a); if(n==1) printf("\n palindrome"); else printf("\n not palindrome"); getch(); }


Design a algorithm to check whether a given string is palindrome or not?

#include <stdio.h> #include <conio.h> #include <string.h> void input(char a[ ]) { int i; printf("\n enter string\n"); scanf("%s",a); } void output(char a[ ]) { printf("\n string is %s",a); } int palindrome(char a[ ]) { int n,i; n=count(a); n=n-1; i=0; for(;a[n]==a[i] && n>=i;i++,n--); if(n>=i) return 0; else return 1; } void main( ) { char a[80],b[80],s; int n; printf("\n check palindrome"); input(a); n=palindrome(a); output(a); if(n==1) printf("\n palindrome"); else printf("\n not palindrome"); getch(); }


Design an algorithm to check whether a given string is a palindrome or not?

#include <stdio.h> #include <conio.h> #include <string.h> void input(char a[ ]) { int i; printf("\n enter string\n"); scanf("%s",a); } void output(char a[ ]) { printf("\n string is %s",a); } int palindrome(char a[ ]) { int n,i; n=count(a); n=n-1; i=0; for(;a[n]==a[i] && n>=i;i++,n--); if(n>=i) return 0; else return 1; } void main( ) { char a[80],b[80],s; int n; printf("\n check palindrome"); input(a); n=palindrome(a); output(a); if(n==1) printf("\n palindrome"); else printf("\n not palindrome"); getch(); }


Which palindrome is a preposition?

Ere is a preposition that is a palindrome.


Is glockenspiel a palindrome?

No, it isn't a palindrome.


What is the palindrome of balanced?

The palindrome is Level.


Using Python write an algorithm that takes a string as input and determines whether or not it is a palindrome?

def isPalindrome(s): return s == s[::-1] then just call the function with a string like isPalindrome('poop')


Which 4 digit number is always a palindrome?

Any number that is is a palindrome will always be a palindrome.


Is 107541 a palindrome?

No. A palindrome reads the same backwards and forwards. 5791111975 is an example of a palindrome.


What is a palindrome for a musical engagement?

The palindrome is Gig.


What is a palindrome for plastic?

"Saltcaps" is a palindrome for plastic.