Question

Convert the given string into palindrome with minimum number of appends(at end of the given string). O(n) algorithm will be appreciated ??

Input :=> Malayal
Output :=> Malayalam

Answer 1

remove one char one by one and see if remaining string is palindrome or not.

int palindrome(char* string)
{
    size_t len = strlen(string);

    // handle empty string and string of length 1:
    if (len == 0) return 0;
    if (len == 1) return 1;

    char *ptr1 = string;
    char *ptr2 = string + len - 1;
    while(ptr2 >= ptr1) {
        if (!isalpha(*ptr2)) {
            ptr2--;
            continue;
        }
        if (!isalpha(*ptr1)) {
            ptr1++;
            continue;
        }
        if( tolower(*ptr1) != tolower(*ptr2)) {
            return 0;
        }
        ptr1++; ptr2--;
    }
    return 1;
} 

int findMinAppend(char str[])
{
    if (palindrome(str)) 
        return 0;
    else 
    {
        str++;
        return 1 + findMinAppend(str);
    }
}

int main()
{
    char str[] = "malayal";
    printf("%d", findMinAppend(str));
    return 0;
}