<Codesignal> buildPalindrome

Medium

Given a string, find the shortest possible string which can be achieved by adding characters to the end of initial string to make it a palindrome.

Example

For st = "abcdc", the output should be
buildPalindrome(st) = "abcdcba".

Input/Output

• [execution time limit] 0.5 seconds (c)

• [input] string st

  A string consisting of lowercase English letters.

  Guaranteed constraints:
  3 ≤ st.length ≤ 10.

• [output] string

[C] Syntax Tips

// Prints help message to the console
// Returns a string
char * helloWorld(char * name) {
    char * answer = malloc(strlen(name) + 8);
    printf("This prints to the console when you Run Tests");
    strcpy(answer, "Hello, ");
    strcat(answer, name);
    return answer;
}

---

Solution

char *buildPalindrome(char *st)
{
	int N=strlen(st);

	for(int i=0;i<N;i++)
	{
		bool palindrome=true;

		if(st[i]==st[N-1])
		{
			for(int j=1;i+j<N-1;j++)
				if(st[i+j]!=st[N-j-1])
				{
					palindrome=false;
					break;
				}

			if(palindrome)
			{
				for(int j=i-1;j>=0;j--)
					st[N++]=st[j];

				st[N]='\0';
				return st;
			}
		}
	}
}