Reversing a linked list in cpp

Data Structures/Linked List/Sorting_linked_list.cpp

@@ -0,0 +1,69 @@
+
+struct ListNode {
+    int val;
+    ListNode *next;
+    ListNode(int x) : val(x), next(NULL) {}
+    };
+ListNode* merge(ListNode* A, ListNode* B){
+    if(A == NULL){
+        return B;
+    }
+    if(B == NULL){
+        return A;
+    }
+
+    ListNode* head = NULL;
+
+    if(A->val < B->val){
+        head = A;
+        A = A->next;
+    }
+    else{
+        head = B;
+        B = B->next;
+    }
+
+    ListNode* temp = head;
+
+    while(A != NULL && B != NULL){
+        if(A->val < B->val){
+            temp->next = A;
+            A = A->next;
+        }
+        else{
+            temp->next = B;
+            B = B->next;
+        }
+        temp = temp->next;
+    }
+
+    if(A != NULL){
+        temp->next = A;
+    }
+    else{
+        temp->next = B;
+    }
+
+    return head;
+}
+
+ListNode* Solution::sortList(ListNode* A) {
+    ListNode* head = A;
+
+    if(head == NULL || head->next == NULL){
+        return head;
+    }
+
+    ListNode* start = A;
+    ListNode* end = A->next;
+
+    while(end != NULL && end->next != NULL){
+        start = start->next;
+        end = (end->next)->next;
+    }
+
+    end = start->next;
+    start->next = NULL;
+
+    return merge(sortList(head), sortList(end));
+}