LinkedList

Author: Rashed112

LeetCode Blind 75 solutions/21_merge_two_sorted_lists.cpp

@@ -0,0 +1,54 @@
+/**
+ * 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* mergeTwoLists(ListNode* list1, ListNode* list2) {
+        ListNode *head = NULL;
+        if(list2 == NULL){
+            return list1;
+        }
+        if(list1 == NULL){
+            return list2;
+        }
+        if(list1->val <= list2->val){
+            head = list1;
+            list1 = list1->next;
+        }
+        else{
+            head = list2;
+            list2 = list2->next;
+        }
+        ListNode *curr = head;
+        while(list1 != NULL && list2 != NULL ){
+            if(list1->val <= list2->val){
+                curr->next = list1;
+                list1 = list1->next;
+            }
+            else{
+                curr->next = list2;
+                list2 = list2->next;
+            }
+            curr = curr->next;
+        }
+        if(list1){
+            curr->next = list1;
+        }
+        else{
+            curr->next = list2;
+        }
+        return head;
+
+
+    }
+};
+
+//Time: O(m+n)
+//Space: O(1)