Remove Duplicates from Sorted List II -- leetcode

标签：leetcode   链表   去重   

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.

写法一

设置前后两个指针， 后指针，指向没有重复的最后一个元素。

另一指针指向当前元素。

当遇到重复元素时，一直移动当前指针。

通过判断当前指针有没有移动过，可得知，当前元素是否为重复元素。

如果没有移动，则不是重复元素。接受他，即将后指针指向该元素。

此代码在leetcode上实际运行时间为14ms。

/**
 * 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 fake(0);
        ListNode *last = &fake;
        last->next = head;
        while (head) {
            head = head->next;
            while (head && head->val == last->next->val) {
                auto bak = head->next;
                delete head;
                head = bak;
            }
            
            if (last->next->next == head)
                last = last->next;
            else {
                delete last->next;
                last->next = head;
            }
        }
        
        return fake.next;
    }
};

写法二

此代码在leetcode上实际执行时间为16ms。

判断接下来两个元素是否重复。如果重复，进入重复分支处理。

class Solution {
public:
    ListNode *deleteDuplicates(ListNode *head) {
        ListNode fake(0);
        ListNode *last = &fake;
        last->next = head;
        while (head && head->next) {
            head = head->next;
            if (last->next->val == head->val) {
                while (head && last->next->val == head->val) {
                    last->next->next = head->next;
                    delete head;
                    head = last->next->next;
                }
                delete last->next;
                last->next = head;
            }
            else {
                last = last->next;
            }
        }
        
        return fake.next;
    }
};

Remove Duplicates from Sorted List II -- leetcode

标签：leetcode   链表   去重   

原文地址：http://blog.csdn.net/elton_xiao/article/details/45111815