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leetcode (82, 83) remove duplicates from sorted list i, ii

admin 11月 12, 2020 0

Leetcode 83. Remove Duplicates from Sorted List
Leetcode 82. Remove Duplicates from Sorted List

Remove Duplicates from Sorted List

Leetcode 83. Remove Duplicates from Sorted List

Leetcode 83. Remove Duplicates from Sorted List

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.

class Solution {
public:
    ListNode* deleteDuplicates(ListNode* head) {
        ListNode* prev = head;
        while (prev) {
            if (prev->next && prev->val == prev->next->val)
                prev->next = prev->next->next;
            else
                prev = prev->next;
        }
        
        return head;
    }
};

Leetcode 82. Remove Duplicates from Sorted List

Leetcode 82. Remove Duplicates from Sorted List II

Given a sorted linked list, delete all nodes that have duplicate numbers, leaving only distinct numbers from the original list.

For example,

Given 1->2->3->3->4->4->5, return 1->2->5.

Given 1->1->1->2->3, return 2->3.

/**
 * Definition for singly-linked list.
 * struct ListNode {
 *     int val;
 *     ListNode *next;
 *     ListNode(int x) : val(x), next(NULL) {}
 * };
 */
class Solution {
public:
    ListNode* deleteDuplicates(ListNode* head) {
        ListNode* prevhead = new ListNode(0);
        ListNode* prev = head;
        ListNode* point = prevhead;
        
        while (prev) {
            if (prev->next && prev->val == prev->next->val)
                while (prev->next && prev->val == prev->next->val)
                    prev = prev->next;
            else {
                point->next = prev;
                point = point ->next;
            }
            prev = prev->next;
        }
        point->next = NULL;
        return prevhead->next;
    }
};