Create MergeSort.cpp

Cpp/MergeSort.cpp

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+// Github username: kashika1109
+// Aim: Merge sort using Linked List in C++
+// Date: 10 October 2022
+
+
+//{ Driver Code Starts
+#include <iostream>
+#include <stdio.h>
+#include <stdlib.h>
+#include <bits/stdc++.h>
+using namespace std;
+
+struct Node {
+    int data;
+    struct Node* next;
+    Node(int x) {
+        data = x;
+        next = NULL;
+    }
+};
+
+
+// } Driver Code Ends
+/* Structure of the linked list node is as
+struct Node 
+{
+    int data;
+    struct Node* next;
+    Node(int x) { data = x;  next = NULL; }
+};
+*/
+
+
+class Solution{
+  public:
+    //Function to sort the given linked list using Merge Sort.
+Node* midpoint(Node *head){ //MIDPOINT OF LINKED LIST
+Node *slow=head;
+Node *fast=head->next;
+while(fast!=NULL && fast->next!=NULL){
+	slow=slow->next;
+	fast=fast->next->next;
+}
+return slow;
+}
+
+Node* merge(Node *h1,Node *h2){ //MERGING TWO LINKED LIST
+	 if(h1==NULL)
+            return h2;
+        if(h2==NULL)
+            return h1;
+	Node *fhead=NULL;
+	Node *ftail=NULL;
+	if(h1->data <= h2->data){
+		fhead=h1;
+		ftail=h1;
+		h1=h1->next;
+		}
+		else{
+			fhead=h2;
+			ftail=h2;
+			h2=h2->next;
+		}
+	while(h1!=NULL && h2!=NULL){
+		if(h1->data <= h2->data){
+		ftail->next=h1;
+		ftail=h1;
+		h1=h1->next;
+		}
+		else{
+		ftail->next=h2;
+		ftail=h2;
+		h2=h2->next;	
+		}
+	}
+	if(h1==NULL){
+		ftail->next=h2;
+	} else if(h2==NULL){
+		ftail->next=h1;
+	}
+
+	return fhead;
+}
+
+Node* mergeSort(Node *head){           //MERGESORT
+	if(head==NULL || head->next==NULL) return head;
+	Node *mid=midpoint(head); 
+	Node *head1=head; 
+	Node *head2=mid->next;  
+	mid->next=NULL; 
+	Node *left_LL=mergeSort(head1); 
+	Node *right_LL=mergeSort(head2); 
+	Node *finalHead=merge(left_LL,right_LL);
+	return finalHead;
+}
+
+};
+
+
+//{ Driver Code Starts.
+
+void printList(Node* node) {
+    while (node != NULL) {
+        printf("%d ", node->data);
+        node = node->next;
+    }
+    printf("\n");
+}
+
+void push(struct Node** head_ref, int new_data) {
+    Node* new_node = new Node(new_data);
+
+    new_node->next = (*head_ref);
+    (*head_ref) = new_node;
+}
+
+int main() {
+    long test;
+    cin >> test; //input testcases
+    while (test--) { //while testcases exist
+        struct Node* a = NULL;
+        long n, tmp;
+        cin >> n;
+        for (int i = 0; i < n; i++) { 
+            cin >> tmp;
+            push(&a, tmp);
+        }
+        Solution obj;
+        a = obj.mergeSort(a);
+        printList(a); 
+    }
+    return 0;
+}
+// } Driver Code Ends