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Add Sort singly linked list #2507

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Add Sort singly linked list #2507

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107 changes: 107 additions & 0 deletions DataStructures/Lists/SortSinglyLinkedList.java
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Original file line number Diff line number Diff line change
@@ -0,0 +1,107 @@
class ListNode {
int val;
ListNode next;

ListNode() {
}

ListNode(int val) {
this.val = val;
}

ListNode(int val, ListNode next) {
this.val = val;
this.next = next;
}
}

public class SortSinglyLinkedList {

//Driver function
public static void main(String[] args) {
ListNode dummy = new ListNode();
ListNode temp = dummy;
for (int i = 10; i > 0; i--) {
temp.next = new ListNode(i);
temp = temp.next;
}
temp = dummy.next;
print(temp);
temp = sortList(temp);
print(temp);
}

public static ListNode sortList(ListNode head) {
if (head == null || head.next == null) {
return head;
}

ListNode middle = middle(head);
ListNode next = middle.next;
middle.next = null;
return mergeTwoLists(sortList(head), sortList(next));
}

private static ListNode mergeTwoLists(ListNode l1, ListNode l2) {

if (l1 == null) {
return l2;
}
if (l2 == null) {
return l1;
}

ListNode temp, head;
if (l1.val <= l2.val) {
temp = l1;
l1 = l1.next;
} else {
temp = l2;
l2 = l2.next;
}

head = temp;

while (l1 != null && l2 != null) {
if (l1.val <= l2.val) {
temp.next = l1;
temp = temp.next;
l1 = l1.next;
} else {
temp.next = l2;
temp = temp.next;
l2 = l2.next;
}
}

if (l1 != null) {
temp.next = l1;
} else {
temp.next = l2;
}
return head;
}

private static ListNode middle(ListNode head) {
ListNode prev = null;
ListNode temp = head;
ListNode slow = head;

while (temp != null && temp.next != null) {
prev = slow;
slow = slow.next;
temp = temp.next.next;
}
return prev;
}

private static void print(ListNode head) {
ListNode temp = head;
while (temp.next != null) {
System.out.print(temp.val + " -> ");
temp = temp.next;
}
System.out.println(temp.val);
}

}