Introduction:
The Turn It problem on Codechef is a classic example of a problem that requires a simple implementation of a mathematical concept. The problem statement is to find the number of times a given string of characters must be rotated in order to obtain the lexicographically smallest string. In this article, we will be discussing the solution to this problem in the C programming language, with code examples and explanations.
Problem Statement:
Given a string S, the task is to find the number of times S must be rotated in order to obtain the lexicographically smallest string. A rotation operation is defined as taking the last character of the string and placing it at the front of the string. For example, if S = 'abcde', then S rotated 1 time would be 'eabcd' and S rotated 2 times would be 'deabc'.
Solution:
The key to solving this problem is understanding the concept of lexicographic order. In simple terms, lexicographic order is the order in which words are arranged in a dictionary. For example, in the English language, 'apple' comes before 'banana' because 'a' comes before 'b' in the alphabet.
In the context of this problem, we need to find the lexicographically smallest string by rotating the given string multiple times. The easiest way to do this is to find the lexicographically smallest character in the string and rotate the string until that character is at the front.
One way to implement this in C is to use a for loop to iterate through the string and find the lexicographically smallest character. Once the smallest character is found, we can use another for loop to rotate the string until the smallest character is at the front.
Code Example:
#include <stdio.h>
#include <string.h>
int main()
{
char s[100];
int n, i, j, k, count = 0;
scanf("%s", s);
n = strlen(s);
for(i = 0; i < n; i++)
{
for(j = i+1; j < n; j++)
{
if(s[j] < s[i])
{
char temp = s[i];
s[i] = s[j];
s[j] = temp;
count++;
}
}
}
printf("%d", count);
return 0;
}
Explanation:
In the above code, we first take the input string and store it in the 's' character array. We then use the strlen() function to find the length of the string, which is stored in the 'n' variable.
We then use a nested for loop to iterate through the string and compare the characters at each index. If the character at the current index 'j' is lexicographically smaller than the character at the previous index 'i', we swap the characters and increment the count variable.
Finally, we print the value of the count variable, which will be the number of times the string needs to be rotated to obtain the lexicographically smallest string.
Note: In the above code snippet, we are assuming that the input strings are lowercase. If the input strings can contain uppercase characters, then you should use strlwr() function to convert the string to lowercase before using the above solution.
Conclusion:
The Turn It problem on Codechef is a simple
and related concepts that can help in solving similar problems.
One related concept is the use of the KMP algorithm for pattern matching. The KMP (KnuthMorrisPratt) algorithm is an efficient algorithm for finding patterns in strings. It uses preprocessing to create a partial match table that can be used to skip over characters that do not match the pattern. This can be useful in solving problems where you need to find patterns in strings, such as finding all occurrences of a substring in a larger string.
Another related concept is the use of the ZAlgorithm for string matching. The ZAlgorithm is a lineartime algorithm that can be used to find all occurrences of a pattern in a string. It uses a Zarray, which stores the length of the longest common prefix between the pattern and the substring starting at each position in the string. This can be useful in solving problems where you need to find patterns in strings, such as finding all occurrences of a substring in a larger string.
Both KMP and Z algorithm are linear time algorithm, but Zalgorithm is little simpler and easy to implement.
Both of these concepts can be used in combination with the solution discussed in this article to solve more complex string manipulation problems. For example, you could use the KMP or Z algorithm to find all occurrences of a pattern in a string, and then use the solution discussed in this article to find the lexicographically smallest string that contains that pattern.
In conclusion, the Turn It problem on Codechef is a simple problem that can be solved using basic string manipulation techniques. However, understanding related concepts such as the KMP and Z algorithm can help in solving more complex string manipulation problems.
Popular questions

What is the problem statement of the Turn It problem on Codechef?
Answer: The problem statement is to find the number of times a given string of characters must be rotated in order to obtain the lexicographically smallest string. 
How is a rotation operation defined in the context of the Turn It problem?
Answer: A rotation operation is defined as taking the last character of the string and placing it at the front of the string. For example, if S = 'abcde', then S rotated 1 time would be 'eabcd' and S rotated 2 times would be 'deabc'. 
What is the key concept to solving the Turn It problem?
Answer: The key concept is understanding the concept of lexicographic order. We need to find the lexicographically smallest string by rotating the given string multiple times. 
How can the KMP algorithm be used to solve similar problems?
Answer: The KMP (KnuthMorrisPratt) algorithm is an efficient algorithm for finding patterns in strings. It uses preprocessing to create a partial match table that can be used to skip over characters that do not match the pattern. This can be useful in solving problems where you need to find patterns in strings, such as finding all occurrences of a substring in a larger string. 
How can the Zalgorithm be used to solve similar problems?
Answer: The Zalgorithm is a lineartime algorithm that can be used to find all occurrences of a pattern in a string. It uses a Zarray, which stores the length of the longest common prefix between the pattern and the substring starting at each position in the string. This can be useful in solving problems where you need to find patterns in strings, such as finding all occurrences of a substring in a larger string.
Tag
StringManipulation