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# Python3 Program to Rotate the sub-list of a linked list from position M to N to the right by K places

Given a linked list and two positions ‘m’ and ‘n’. The task is to rotate the sublist from position m to n, to the right by k places. Examples:

Input: list = 1->2->3->4->5->6, m = 2, n = 5, k = 2 Output: 1->4->5->2->3->6 Rotate the sublist 2 3 4 5 towards right 2 times then the modified list are: 1 4 5 2 3 6 Input: list = 20->45->32->34->22->28, m = 3, n = 6, k = 3 Output: 20->45->34->22->28->32 Rotate the sublist 32 34 22 28 towards right 3 times then the modified list are: 20 45 34 22 28 32

## Recommended: Please try your approach on {IDE} first, before moving on to the solution.

Approach: For rotating the given sublist that extends from m to n element, move the list from (n-k+1)th to nth node to starting of sub-list to finish the rotation. If k is greater than size of sublist then we will take its modulo with size of sublist. So traverse through list using a pointer and a counter and we will save (m-1)th node and later make it point to (n-k+1)th node and hence bring (n-k+1)th node to the start(front) of sublist. Similarly we will save mth node and later make nth node point to it. And for keeping rest of list intact we will make (n-k)th node point to next node of n (maybe NULL). And finally we will get the k times right rotated sublist. Below is the implementation of the above approach:

## Python3

 `# Python3 implementation of the above approach``import` `math` `# Definition of node of linkedlist``class` `Node:``    ``def` `__init__(``self``, data):``        ``self``.data ``=` `data``        ``self``.``next` `=` `None` `# This function take head pointer of list,``# start and end points of sublist that is``# to be rotated and the number k and``# rotate the sublist to right by k places.``def` `rotateSubList(A, m, n, k):``    ``size ``=` `n ``-` `m ``+` `1` `    ``# If k is greater than size of sublist then``    ``# we will take its modulo with size of sublist``    ``if` `(k > size):``        ``k ``=` `k ``%` `size``    ` `    ``# If k is zero or k is equal to size or k is``    ``# a multiple of size of sublist then list``    ``# remains intact``    ``if` `(k ``=``=` `0` `or` `k ``=``=` `size):``        ``head ``=` `A``        ``while` `(head !``=` `None``):``            ``print``(head.data)``            ``head ``=` `head.``next``        ` `        ``return``    ` `    ``link ``=` `None` `# m-th node``    ``if` `(m ``=``=` `1``) :``        ``link ``=` `A``    ` `    ``# This loop will traverse all node till``    ``# end node of sublist.``    ``c ``=` `A ``# Current traversed node``    ``count ``=` `0` `# Count of traversed nodes``    ``end ``=` `None``    ``pre ``=` `None` `# Previous of m-th node``    ``while` `(c !``=` `None``) :``        ``count ``=` `count ``+` `1` `        ``# We will save (m-1)th node and later``        ``# make it point to (n-k+1)th node``        ``if` `(count ``=``=` `m ``-` `1``) :``            ``pre ``=` `c``            ``link ``=` `c.``next``        ` `        ``if` `(count ``=``=` `n ``-` `k) :``            ``if` `(m ``=``=` `1``) :``                ``end ``=` `c``                ``A ``=` `c.``next``            ` `            ``else` `:``                ``end ``=` `c` `                ``# That is how we bring (n-k+1)th``                ``# node to front of sublist.``                ``pre.``next` `=` `c.``next``            ` `        ``# This keeps rest part of list intact.``        ``if` `(count ``=``=` `n) :``            ``d ``=` `c.``next``            ``c.``next` `=` `link``            ``end.``next` `=` `d``            ``head ``=` `A``            ``while` `(head !``=` `None``) :``                ``print``(head.data, end ``=` `" "``)``                ``head ``=` `head.``next``            ` `            ``return``        ` `        ``c ``=` `c.``next``    ` `# Function for creating and linking new nodes``def` `push(head, val):``    ``new_node ``=` `Node(val)``    ``new_node.data ``=` `val``    ``new_node.``next` `=` `head``    ``head ``=` `new_node``    ``return` `head` `# Driver code``if` `__name__``=``=``'__main__'``:``    ``head ``=` `None``    ``head ``=` `push(head, ``70``)``    ``head ``=` `push(head, ``60``)``    ``head ``=` `push(head, ``50``)``    ``head ``=` `push(head, ``40``)``    ``head ``=` `push(head, ``30``)``    ``head ``=` `push(head, ``20``)``    ``head ``=` `push(head, ``10``)``    ``tmp ``=` `head``    ``print``(``"Given List: "``, end ``=` `"")``    ``while` `(tmp !``=` `None``) :``        ``print``(tmp.data, end ``=` `" "``)``        ``tmp ``=` `tmp.``next``    ` `    ``print``()` `    ``m ``=` `3``    ``n ``=` `6``    ``k ``=` `2``    ``print``(``"After rotation of sublist: "``, end ``=` `"")``    ``rotateSubList(head, m, n, k)` `# This code is contributed by Srathore`

Output:

```Given List: 10 20 30 40 50 60 70
After rotation of sublist: 10 20 50 60 30 40 70```

Time complexity: O(N) where N is the size of the given linked list

Auxiliary space: O(1) because it is using constant space

Please refer complete article on Rotate the sub-list of a linked list from position M to N to the right by K places for more details!

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