Javascript Program For QuickSort On Singly Linked List

Last Updated : 09 Sep, 2024

QuickSort on Doubly Linked List is discussed here. QuickSort on Singly linked list was given as an exercise. The important things about implementation are, it changes pointers rather swapping data and time complexity is same as the implementation for Doubly Linked List.

sorting image

In partition(), we consider last element as pivot. We traverse through the current list and if a node has value greater than pivot, we move it after tail. If the node has smaller value, we keep it at its current position.

In QuickSortRecur(), we first call partition() which places pivot at correct position and returns pivot. After pivot is placed at correct position, we find tail node of left side (list before pivot) and recur for left list. Finally, we recur for right list.

JavaScript

// Javascript program for Quick Sort on  // Singly LinKed List  // Sort a linked list using quick sort class Node {     constructor(val) {         this.data = val;         this.next = null;     } }  let head;  function addNode(data) {     if (head == null) {         head = new Node(data);         return;     }      let curr = head;     while (curr.next != null)         curr = curr.next;      let newNode = new Node(data);     curr.next = newNode; }  function printList(n) {     while (n != null) {         console.log(n.data);         n = n.next;     } }  // Takes first and last node, // but do not break any links in // the whole linked list function partitionLast(start, end) {     if (start == end ||         start == null ||         end == null)         return start;      let pivot_prev = start;     let curr = start;     let pivot = end.data;      // Iterate till one before the end,     // no need to iterate till the end     // because end is pivot     while (start != end) {         if (start.data < pivot) {             // Keep tracks of last modified              // item             pivot_prev = curr;             let temp = curr.data;             curr.data = start.data;             start.data = temp;             curr = curr.next;         }         start = start.next;     }      // Swap the position of curr i.e.     // next suitable index and pivot     let temp = curr.data;     curr.data = pivot;     end.data = temp;      // Return one previous to current     // because current is now pointing     // to pivot     return pivot_prev; }  function sort(start, end) {     if (start == null ||         start == end ||         start == end.next)         return;      // Split list and partition recurse     let pivot_prev = partitionLast(start, end);     sort(start, pivot_prev);      // If pivot is picked and moved to the start,     // that means start and pivot is same     // so pick from next of pivot     if (pivot_prev != null &&         pivot_prev == start)         sort(pivot_prev.next, end);      // If pivot is in between of the list,     // start from next of pivot,     // since we have pivot_prev, so we move two nodes     else if (pivot_prev != null &&         pivot_prev.next != null)         sort(pivot_prev.next.next, end); }  // Driver Code addNode(30); addNode(3); addNode(4); addNode(20); addNode(5);  let n = head; while (n.next != null)     n = n.next;  console.log("Linked List before sorting"); printList(head); sort(head, n); console.log("Linked List after sorting"); printList(head); // This code is contributed by umadevi9616

Output

Linked List before sorting 30 3 4 20 5 Linked List after sorting 3 4 5 20 30

Time Complexity: O(N * log N), It takes O(N²) time in the worst case and O(N log N) in the average or best case.

Please refer complete article on QuickSort on Singly Linked List for more details!

Javascript Program For Recursive Selection Sort For Singly Linked List - Swapping Node Links

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