Remove Linked List Elements Problem & Solution
Given the head
of a linked list and an integer val
, remove all the nodes of the linked list that has Node.val == val
, and return the new head
.
See the remove linked list elements problem on LeetCode.
C++ Solution
#pragma GCC optimize("Ofast")
#pragma GCC optimization("unroll-loops")
static const int _=[](){std::ios::sync_with_stdio(false);cin.tie(nullptr);cout.tie(nullptr);return 0;}();
/**
* 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* removeElements(ListNode* head, int val) {
ListNode dummy(INT_MAX, head);
ListNode* prev = &dummy;
ListNode* cursor = head;
while (cursor != nullptr) {
if (cursor->val == val) {
ListNode* tmp = cursor;
prev->next = cursor->next;
// Must update head if deleting the first element.
if (cursor == head) {
head = cursor->next;
}
cursor = cursor->next;
delete tmp;
} else {
prev = cursor;
cursor = cursor->next;
}
}
return head;
}
};
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