Linklist leetcode DSA question no. 23

Merge_k_Sorted_Lists.cpp

@@ -0,0 +1,46 @@
+/**
+ * Definition for singly-linked list.
+ * struct ListNode {
+ *     int val;
+ *     ListNode *next;
+ *     ListNode() : val(0), next(nullptr) {}
+ *     ListNode(int x) : val(x), next(nullptr) {}
+ *     ListNode(int x, ListNode *next) : val(x), next(next) {}
+ * };
+ */
+class Solution {
+public:
+    ListNode* merge(ListNode* l1, ListNode* l2){
+        ListNode* ans = new ListNode(-1);
+        ListNode* temp = ans;
+        while(l1!=NULL &&  l2!=NULL){
+            if(l1->val >l2->val){
+                temp->next = l2;
+                temp =l2;
+                l2= l2->next;
+            }
+            else{
+                temp->next = l1;
+                temp =l1;
+                l1= l1->next;
+            }
+        }
+        if(l1){
+            temp->next = l1;
+        }
+        if(l2){
+            temp->next = l2;
+        }
+        return ans->next;
+    }
+    ListNode* mergeKLists(vector<ListNode*>& lists) {
+        if(lists.size()==0){
+            return NULL;
+        }
+        ListNode* head = lists[0];
+        for(int i=1;i<lists.size();i++){
+            head = merge(head, lists[i]);
+        }
+        return head;
+    }
+};