[t102] Check Palindrome (Medium)

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

int main()
{
    char A[100010];
    scanf("%[^\n]", A);
    int n = strlen(A);
    int i = 0, j = n-1;
    int ok = 1;
    while (i < j) {
        if (!isalpha(A[i])) ++i;
        else if (!isalpha(A[j])) --j;
        else if (tolower(A[i]) != tolower(A[j])) {
            ok = 0;
            break;
        }
        else ++i, --j;
    }
    printf("%s\n", ok ? "YES" : "NO");
    return 0;
}