longestPalindrom

#include<stdio.h>
#include<string.h>

char toLower(char letter){
    return (letter>='a' && letter<='z') ? letter : letter+'a'-'A';
}

int isPalindrom(char *start, char *end){
    if(start>end || (start==end && toLower(*start)==toLower(*end)))return 1;
    else if(toLower(*start)!=toLower(*end))return 0;
    return isPalindrom(start+1,end-1);
}

void longestPalindrom(char *sen){
    char *end=sen+strlen(sen)-1;
    //Helping pointers
    char *start,*helpEnd,*finalStart=sen+1,*finalEnd=sen;

    for(start=sen;start<=end;start++){
        for(helpEnd=end;helpEnd>=start && !isPalindrom(start,helpEnd);helpEnd--);
        if(helpEnd>start && (helpEnd-start)>(finalEnd-finalStart))
            finalEnd=helpEnd,finalStart=start;
    }

    for(;finalStart<=finalEnd;finalStart++)
        printf("%c",*finalStart);
}

int main(){
    //Test
    longestPalindrom("");
    longestPalindrom("yxpxYstsyxpx");
    return 0;
}