Add files via upload

ishankaggarwal · web-flow · commit 602682b038f4 · 2022-04-08T15:09:15.000-07:00
diff --git a/cpp/23-Merge-K-Sorted-Lists.cpp b/cpp/23-Merge-K-Sorted-Lists.cpp
@@ -0,0 +1,51 @@
+/**
+ * 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 compare{
+    public:
+        bool operator()(ListNode* a,ListNode* b){
+            return a->val>b->val;
+        }
+};
+
+class Solution {
+public:
+    ListNode* mergeKLists(vector<ListNode*>& lists) {
+        
+        priority_queue<ListNode*,vector<ListNode*>,compare> pq;
+        
+        for(int i=0;i<lists.size();i++){
+            if(lists[i]!=NULL){
+                pq.push(lists[i]);
+            }
+        }
+        
+        if(pq.empty()){
+            return NULL;
+        }
+        
+        ListNode* dummy=new ListNode;
+        ListNode* last=dummy;
+        
+        while(!pq.empty()){
+            ListNode* curr=pq.top();
+            pq.pop();
+            
+            last->next=curr;
+            last=last->next;
+            
+            if(curr->next!=NULL){
+                pq.push(curr->next);
+            }
+        }
+        return dummy->next;
+    }
+};
