leetcode 203 Remove Linked List Elements



Remove all elements from a linked list of integers that have valueval.

Example
Given: 1 --> 2 --> 6 --> 3 --> 4 --> 5 --> 6, val = 6
Return: 1 --> 2 --> 3 --> 4 --> 5

我的解法：

// Linklist.cpp : Defines the entry point for the console application.
//

#include "stdafx.h"


#include<iostream>
using namespace std;


  struct ListNode
  {
      int val;
      ListNode *next;
      ListNode(int x) : val(x), next(NULL) {}
  };
 


    ListNode* removeElements(ListNode* head, int val) 
    {
        if(head == NULL)return head;
        
        ListNode* pre = NULL;
        ListNode* root = head;
        ListNode* current = head;
        
        
        while(current!=NULL)
        {
            
            if(current->val == val)
            {
                if(pre==NULL)
                {
					current = current->next;
                    root = current;
                    

                }
                else
                {
                    pre->next = current->next;
                    current = current->next;
                    
                }
                
               
            }
            else
            {
                pre = current;
                current =current->next;
                
                
            }
        }
        
        return root;
    }

int _tmain(int argc, _TCHAR* argv[])
{
	ListNode* temp = new ListNode(2);
	ListNode* temp_next = new ListNode(1);
	temp->next = temp_next;
	removeElements(temp,1);
	return 0;
}

python的解法：

class Solution:
    # @param {ListNode} head
    # @param {integer} val
    # @return {ListNode}
    def removeElements(self, head, val):
        dummy = ListNode(-1)
        dummy.next = head

        prev = dummy
        while head:
            if head.val == val:
                prev.next = head.next
                head = prev
            prev = head
            head = head.next
        return dummy.next

一个非常简洁的解法：

struct ListNode* removeElements(struct ListNode* head, int val) 
{
    if (head&&head->val==val)head=removeElements(head->next, val);
    if (head&&head->next)head->next=removeElements(head->next, val);
    return head;
}