19. Remove Nth Node From End of List
Given the head of a linked list, remove the nth node from the end of the list and return its head.
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Input: head = [1,2,3,4,5], n = 2
Output: [1,2,3,5]
Example 2:
Input: head = [1], n = 1
Output: []
Example 3:
Input: head = [1,2], n = 1
Output: [1]
C++ Solution
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ListNode* removeNthFromEnd(ListNode* head, int n) {
ListNode* ptr = head;
int len = 0;
while (ptr != nullptr) {
len++;
ptr = ptr->next;
}
int index = len - n - 1;
ListNode *guard = new ListNode();
guard->next = head;
ptr = guard;
int i = -1;
while (i < index) {
ptr = ptr->next;
i++;
}
auto removeNode = ptr->next;
if (removeNode != nullptr) {
ptr->next = removeNode->next;
}
return guard->next;
}
