Remove Duplicates from Sorted List
描述
Given a sorted linked list, delete all duplicates such that each element appear only once.
For example,
Given 1->1->2, return 1->2.
Given 1->1->2->3->3, return 1->2->3.
分析
无
递归版
// Remove Duplicates from Sorted List
// 递归版，时间复杂度O(n)，空间复杂度O(1)
class Solution {
public:
ListNode *deleteDuplicates(ListNode *head) {
if (!head) return head;
ListNode dummy(head->val + 1); // 值只要跟head不同即可
dummy.next = head;
recur(&dummy, head);
return dummy.next;
}
private:
static void recur(ListNode *prev, ListNode *cur) {
if (cur == nullptr) return;
if (prev->val == cur->val) { // 删除head
prev->next = cur->next;
delete cur;
recur(prev, prev->next);
} else {
recur(prev->next, cur->next);
}
}
};迭代版
// Remove Duplicates from Sorted List
// 迭代版，时间复杂度O(n)，空间复杂度O(1)
class Solution {
public:
ListNode *deleteDuplicates(ListNode *head) {
if (head == nullptr) return nullptr;
for (ListNode *prev = head, *cur = head->next; cur != nullptr; cur = prev->next) {
if (prev->val == cur->val) {
prev->next = cur->next;
delete cur;
} else {
prev = cur;
}
}
return head;
}
};