Python Program to find minimum number of rotations to obtain actual string
Given two strings s1 and s2. The task is to find out the minimum number of string rotations for the given string s1 to obtain the actual string s2. Examples:
Input : eeksg, Beginner Output: 1 Explanation: g is rotated left to obtain Beginner. Input : eksge, Beginner Output: 2 Explanation : e and g are left rotated to obtain Beginner.
Approach:
- Use string slicing to rotate the string.
- Perform right rotations str1=str1[1:len(str1)]+str1[0] on string to obtain the actual string.
- Perform left rotations m=m[len(m)-1]+m[:len(m)-1] on string to obtain the actual string.
- Print the minimum of left(x) and right(y) rotations.
TIME COMPLEXITY: O(n) Below is the implementation:
python3
def findRotations(str1, str2): # To count left rotations # of string x = 0 # To count right rotations # of string y = 0 m = str1 while True : # left rotating the string m = m[ len (m) - 1 ] + m[: len (m) - 1 ] # checking if rotated and # actual string are equal. if (m = = str2): x + = 1 break else : x + = 1 if x > len (str2) : break while True : # right rotating the string str1 = str1[ 1 : len (str1)] + str1[ 0 ] # checking if rotated and actual # string are equal. if (str1 = = str2): y + = 1 break else : y + = 1 if y > len (str2): break if x < len (str2): # printing the minimum # number of rotations. print ( min (x,y)) else : print ("given strings are not of same kind") # Driver code findRotations( 'sgeek' , 'Beginner' ) |
Output:
1
The Time and Space Complexity for all the methods are the same:
Time Complexity: O(n)
Auxiliary Space: O(n)
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