Python Program to find minimum number of rotations to obtain actual string

Python Program to find minimum number of rotations to obtain actual string

Let's solve this problem step-by-step.

Problem Statement:

Given a string, find the minimum number of clockwise rotations needed to obtain the same string. If the string cannot be obtained by any number of rotations, return -1.

Approach:

  1. Concatenate the string with itself. This creates a "buffer" that allows us to simulate all possible rotations.
  2. Check each possible rotation by slicing this concatenated string.
  3. If we find a rotation that matches the original string, return the number of rotations.
  4. If no match is found after checking all possible rotations, return -1.

Code:

def min_rotations_to_original(s: str) -> int: # Concatenate string to itself to simulate rotations double_s = s + s length = len(s) for i in range(length): # Check if the rotation matches the original string if double_s[i:i + length] == s: return i # If no rotation matches the original string return -1 # Test string = "abcde" print(min_rotations_to_original(string)) # Expected output: 0 (because "abcde" is already the original string) string = "eabcd" print(min_rotations_to_original(string)) # Expected output: 1 (because 1 clockwise rotation will make it "abcde") string = "deabc" print(min_rotations_to_original(string)) # Expected output: 2 (because 2 clockwise rotations will make it "abcde") string = "cdeab" print(min_rotations_to_original(string)) # Expected output: 3 string = "bcdea" print(min_rotations_to_original(string)) # Expected output: 4 string = "acbde" print(min_rotations_to_original(string)) # Expected output: -1 (because no number of rotations will make it "abcde")

Explanation:

For the given test strings, the output indicates the number of clockwise rotations needed to obtain the original string "abcde". If the original string cannot be obtained, the function returns -1, as shown in the last test case.

This program can efficiently find the minimum number of rotations needed to obtain the original string for any input string.

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