125.c

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

charch2lower(charch) {
if (ch >= 'A'&&ch <= 'Z')
ch+=0x20;

returnch;
}

boolisPalindrome(char*s) {
intlen=strlen(s);
inthead, tail;
head=tail=0;
tail=len-1;

while (head <= tail) {
while (ch2lower(s[head]) <'0'
|| (ch2lower(s[head]) >'9'&&ch2lower(s[head]) <'a')
||ch2lower(s[head]) >'z')
 {
head++;
if (head>tail) break;
 }

while (ch2lower(s[tail]) <'0'
|| (ch2lower(s[tail]) >'9'&&ch2lower(s[tail]) <'a')
||ch2lower(s[tail]) >'z')
 {
tail--;
if (head>tail) break;
 }

if (head>tail) break;

if (ch2lower(s[head]) !=ch2lower(s[tail])) return false;

head++;
tail--;
 }

return true;
}

intmain() {
chars1[] ="A man, a plan, a canal: Panama";
chars2[] ="race a car";
chars3[] ="";
chars4[] ="a";
chars5[] =".,";
chars6[] =".";
chars7[] =" ";

printf("%d\n", isPalindrome(s1));
printf("%d\n", isPalindrome(s2));
printf("%d\n", isPalindrome(s3));
printf("%d\n", isPalindrome(s4));
printf("%d\n", isPalindrome(s5));
printf("%d\n", isPalindrome(s6));
printf("%d\n", isPalindrome(s7));

return0;
}