Merge K Sorted Lists Solution

Author: PDKhan

merge-k-sorted-lists/PDKhan.cpp

@@ -0,0 +1,36 @@
+struct Compare{
+    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;
+        ListNode* head = nullptr;
+        ListNode* tail;
+
+        for(ListNode* node : lists){
+            if(node) pq.push(node);
+        }
+
+        while(!pq.empty()){
+            ListNode* node = pq.top();
+
+            pq.pop();
+            if(head == nullptr){
+                head = node;
+                tail = head;
+            }else{
+                tail->next = node;
+                tail = tail->next;
+            }
+
+            if(node->next)
+                pq.push(node->next);
+        }
+
+        return head;
+    }
+};