19 remove nth node from end of list

Author: namratabose32

19-remove-nth-node-from-end-of-list.cpp/19-remove-nth-node-from-end-of-list.cpp

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+/**
+ * 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* removeNthFromEnd(ListNode* head, int n) {
+        int cnt=0;
+        ListNode* curr=head;
+        while(curr){
+            curr=curr->next;
+            cnt++;
+        }curr=head;
+        if(n==1 && cnt==1)
+            return NULL;
+        if(cnt-n==0)
+            return head->next;
+        for(int i=1;i<cnt-n;i++){
+            curr=curr->next;
+        }
+        if(curr->next==NULL)
+            return head;
+        if(curr->next->next==NULL)
+            curr->next=NULL;
+        else
+            curr->next=curr->next->next;
+        return  head;
+    }
+};

19-remove-nth-node-from-end-of-list.cpp/README.md

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+<h2><a href="https://leetcode.com/problems/remove-nth-node-from-end-of-list/">19. Remove Nth Node From End of List</a></h2><h3>Medium</h3><hr><div><p>Given the <code>head</code> of a linked list, remove the <code>n<sup>th</sup></code> node from the end of the list and return its head.</p>
+
+<p>&nbsp;</p>
+<p><strong>Example 1:</strong></p>
+<img alt="" src="https://assets.leetcode.com/uploads/2020/10/03/remove_ex1.jpg" style="width: 542px; height: 222px;">
+<pre><strong>Input:</strong> head = [1,2,3,4,5], n = 2
+<strong>Output:</strong> [1,2,3,5]
+</pre>
+
+<p><strong>Example 2:</strong></p>
+
+<pre><strong>Input:</strong> head = [1], n = 1
+<strong>Output:</strong> []
+</pre>
+
+<p><strong>Example 3:</strong></p>
+
+<pre><strong>Input:</strong> head = [1,2], n = 1
+<strong>Output:</strong> [1]
+</pre>
+
+<p>&nbsp;</p>
+<p><strong>Constraints:</strong></p>
+
+<ul>
+	<li>The number of nodes in the list is <code>sz</code>.</li>
+	<li><code>1 &lt;= sz &lt;= 30</code></li>
+	<li><code>0 &lt;= Node.val &lt;= 100</code></li>
+	<li><code>1 &lt;= n &lt;= sz</code></li>
+</ul>
+
+<p>&nbsp;</p>
+<p><strong>Follow up:</strong> Could you do this in one pass?</p>
+</div>