<p>Given the <code>head</code> of a sorted linked list, <em>delete all nodes that have duplicate numbers, leaving only distinct numbers from the original list</em>. Return <em>the linked list <strong>sorted</strong> as well</em>.</p>

<p>&nbsp;</p>
<p><strong class="example">Example 1:</strong></p>
<img alt="" src="https://assets.leetcode.com/uploads/2021/01/04/linkedlist1.jpg" style="width: 500px; height: 142px;" />
<pre>
<strong>Input:</strong> head = [1,2,3,3,4,4,5]
<strong>Output:</strong> [1,2,5]
</pre>

<p><strong class="example">Example 2:</strong></p>
<img alt="" src="https://assets.leetcode.com/uploads/2021/01/04/linkedlist2.jpg" style="width: 500px; height: 205px;" />
<pre>
<strong>Input:</strong> head = [1,1,1,2,3]
<strong>Output:</strong> [2,3]
</pre>

<p>&nbsp;</p>
<p><strong>Constraints:</strong></p>

<ul>
	<li>The number of nodes in the list is in the range <code>[0, 300]</code>.</li>
	<li><code>-100 &lt;= Node.val &lt;= 100</code></li>
	<li>The list is guaranteed to be <strong>sorted</strong> in ascending order.</li>
</ul>

/**
 * 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 {
private:
    ListNode *deletenode(ListNode *temp, ListNode *head){
        if(temp == head){
            head = head->next;
            delete temp;
            return head;
        }

        ListNode *prev=head;
        ListNode *temp2 = head->next;
        while((temp2 != temp) && (temp2 != NULL)){
            prev = prev->next;
            temp2 = temp2->next;
        }
        if(temp2->next == NULL){
            prev->next = NULL;
        }else{
            prev->next = temp2->next;
        }
        delete temp2;
        return head;
    }
public:
    ListNode* deleteDuplicates(ListNode* head) {
        if(!head || !head->next){
            return head;
        }
        ListNode *temp=head;
        ListNode *curr = NULL;
        while((temp->next != NULL) && (temp != NULL)){
            if(temp->val == temp->next->val){
                curr = temp->next;
                head = deletenode(temp, head);
                temp = curr;
            }else{
                if(curr != NULL){
                    temp = temp->next;
                    head = deletenode(curr, head);
                    curr = NULL;
                }else{
                    temp = temp->next;
                }
            }
        }
        if(curr != NULL){
            temp = temp->next;
            head = deletenode(curr, head);
        }
        return head;
    }
};
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