Hướng dẫn python rotate string

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Given a string of size n, write functions to perform following operations on string.

1. Left (Or anticlockwise) rotate the given string by d elements (where d <= n).
2. Right (Or clockwise) rotate the given string by d elements (where d <= n).

Examples:

Input : s = "GeeksforGeeks"
        d = 2
Output : Left Rotation  : "eksforGeeksGe" 
         Right Rotation : "ksGeeksforGee"  


Input : s = "qwertyu" 
        d = 2
Output : Left rotation : "ertyuqw"
         Right rotation : "yuqwert"

Method 1: We have existing solution for this problem please refer Left Rotation and Right Rotation of a String link. We will solve this problem quickly in python using String Slicing. Approach is very simple,

1. Separate string in two parts first & second, for Left rotation Lfirst = str[0 : d] and Lsecond = str[d :]. For Right rotation Rfirst = str[0 : len(str)-d] and Rsecond = str[len(str)-d : ].
2. Now concatenate these two parts second + first accordingly.

Implementation:

Python3

def rotate(input,d):

    Lfirst = input[0 : d]

    Lsecond = input[d :]

    Rfirst = input[0 : len(input)-d]

    Rsecond = input[len(input)-d : ]

    print ("Left Rotation : ", (Lsecond + Lfirst) )

    print ("Right Rotation : ", (Rsecond + Rfirst))

if __name__ == "__main__":

    input = 'GeeksforGeeks'

    d=2

    rotate(input,d)

Output:

Left Rotation  : eksforGeeksGe 
Right Rotation : ksGeeksforGee

Method 2: We use extended string to rotate the string. We will solve this problem quickly in python by slicing extended string. Approach is very simple,

Use extended string Extend_str, for Left rotation Lfirst = Extended_str[n : l1+n] . For Right rotation Rfirst = str[l1-n : l2-n].
Now print this string. 

Implementation:

Python3

def rotate(str1,n):

    temp = str1 + str1

    l1 = len(str1)

    l2 = len(temp)

    Lfirst = temp[n  : l1+n]

    Lfirst = temp[l1-n : l2-n]

    print ("Left Rotation : ", Lfirst)

    print ("Right Rotation : ", Lfirst )

if __name__ == "__main__":

    input = 'GeeksforGeeks'

    d=2

    rotate(input,d)

Output

Left Rotation :  ksGeeksforGee
Right Rotation :  ksGeeksforGee