vault backup: 2022-06-16 14:32:37

CS notes/pages/Leetcode Remove-Duplicates-From-Sorted-List.md

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+# Leetcode Remove-Duplicates-From-Sorted-List
+
+#### 2022-06-16 14:21
+
+> ##### Data structures:
+> #DS #linked_list 
+> ##### Difficulty:
+> #coding_problem #difficulty-easy 
+> ##### Additional tags:
+> #leetcode
+> ##### Revisions:
+> Initial encounter: 2022-06-16
+
+##### Related topics:
+```expander
+tag:#linked_list
+```
+ 
+ 
+
+##### Links:
+- [Link to problem]()
+___
+### Problem
+
+#### Examples
+
+#### Constraints
+
+### Thoughts
+
+This can be implemented using recursion and iteration, like [[Leetcode Reverse-Linked-List]].
+Recursion is not recommended, since it will take up O(n) space.
+In iteration, one pointer or 2 pointers can be used.
+
+To understand the ptr->next->next = ptr->next, see[[Leetcode Reverse-Linked-List#Solution]]
+
+### Solution
+
+One pointer method
+```cpp
+/**
+ * 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 *deleteDuplicates(ListNode *head) {
+    ListNode *ptr = head;
+    while (ptr != NULL && ptr->next != NULL) {
+      if (ptr->val == ptr->next->val) {
+        // Duplicate found
+        auto tmp = ptr->next;
+        ptr->next = ptr->next->next;
+        delete tmp;
+        // I done set ptr to ptr->next, in case new ptr->next is duplicated
+      } else {
+        ptr = ptr->next;
+      }
+    }
+    return head;
+  }
+};
+```
+