JavaScript program for left and right rotation of strings

String left rotation means moving a given number of characters counterclockwise from the prefix side and adding them to the suffix side. Similarly, right rotation of a string means that the characters of a given string are moved clockwise, but exactly the opposite of left rotation, and a given number of characters are taken from the suffix and added to the prefix of the string. In this article, we will implement a JavaScript program for left rotation and right rotation of a given string.

Problem Introduction

In this question, we get a string and a number. This number represents how many times we have to rotate the rope in either direction. As we have some idea about clockwise and counterclockwise rotation means taking some characters from the start or prefix side or from the end or suffix side from the given string and then remove from it and add to the end of the string.

The length of the string and the frequency of characters in a given string will not change, only the arrangement of the current string will change.

For example, given a string: apple

Then the left rotation of the given string will be as follows -

• apple

• please

• leapp

• eappl

• apple

We can see that the fifth rotation of the given string is the same as the current string, so further rotations are not possible.

The right rotation of the given string will be as follows -

• eappl

• leapp

• please

• PUriya

• apple

We can see that the 5th right rotation of the given string is the same as the initial string, so if we rotate the string further, there will no longer be a different result.

From the above example, we can conclude that by rotating the string to the left or right the number of times its length will eventually result in a string that is the same as the initial string. So if the number of rotations given is greater than the length of the string, then we can take the pattern and it will give exactly the same answer.

method

We have seen the basic example of left and right rotation of a string, now let us discuss it step by step to better understand the code that will be implemented later.

• First we will get the given string in one variable and store the required number of spins in another variable. We can also print them for better comparison.

• We will create two functions, the first for left rotation and the second for right rotation of strings.

• For each function, we will pass the given string and the number of rotation variables as parameters.

• In the left rotation function, we will take the two substrings containing the last k elements and the second remaining element and swap their positions.

• In the right rotation function, we will get two substrings containing the first k elements and the second containing the remaining elements and swap their positions.

Example

// function for left rotation
function left_rotation(str,k){

   // getting prefix elements and remaining elements
   // switiching there place
   var new_str = str.substr(k) + str.substring(0,k);

   // printing the rotated string
   console.log("String after kth left rotation is: " + new_str);
}

// function for right rotation
function right_rotation(str,k){

   // getting suffix elements and remaining elements
   // switiching there place

   var new_str = str.substr(str.length - k) + str.substring(0,str.length-k);
   // printing the rotated string

   console.log("String after kth rigth rotation is: " + new_str);
}

// given string
var str = "apple"
var k = 2

// printing the given string
console.log("The given string is: " + str);

// getting left rotation

left_rotation(str,k);

// getting right rotation
right_rotation(str,k)

Notice

In the above program, the "k" or number of rotations we gave is less than the size of the string, if k is greater than the size of the string, then the above code will give an error, but as follows we have seen in the introduction part To, the rotation after the string length is repeated multiple times can be calculated by getting the mode of the current number given the string length. For safety reasons, we can always do this -

k = k % (str.length)

Here, str is the given string.

Time and space complexity

The time complexity of the above code is O(N), where N is the size of the given string. In the above code, we just take the string characters and break and add them in different ways, making the time complexity linear.

The space complexity of the above code is O(1) because we are not using any extra space, just storing one string into another string, and that space is used for the answer, so no extra space is used. p>

in conclusion

In this tutorial, we implemented a JavaScript program for left rotation and right rotation of a given string. Rotating a string left means moving a given number of characters counterclockwise, and rotating a string right means moving a given number of characters clockwise. We used the concept of substrings by which we break up the string and add a suffix or prefix on the other side. The time complexity of the given program is O(N) and the space complexity is O(1).

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