leecode 解题总结：203. Remove Linked List Elements

#include <iostream>#include <stdio.h>#include <vector>#include <string>using namespace std;/*问题:Remove all elements from a linked list of integers that have value val.ExampleGiven: 1 --> 2 --> 6 --> 3 --> 4 --> 5 --> 6, val = 6Return: 1 --> 2 --> 3 --> 4 --> 5分析:删除链表中等于指定元素的所有结点。关键删除结点的时候考虑在头结点1】待删除的结点在头结点，令之后的结点成为头结点需要记录当前结点的前一个结点，后一个结点，删除当前结点后，令前一个结点指向后一个结点，并令当前结点为后一个结点输入:7(结点个数) 6(待删除元素)1 2 6 3 4 5 62 11 13 11 1 23 12 1 1输出:1 2 3 4 5no result22*/ struct ListNode {     int val;     ListNode *next;     ListNode(int x) : val(x), next(NULL) {} };class Solution {public:    ListNode* removeElements(ListNode* head, int val) {		//头结点为空，直接返回NULL        if(!head)		{			return NULL;		}		ListNode* PRevious = NULL;		ListNode* next = NULL;		ListNode* node = head;		ListNode* newHead = head;		while(node)		{			next = node->next;			//如果当前结点是待删除结点			if(val == node->val)			{				//如果待删除结点的前一个结点存在，那么就重新设定指向				if(previous)				{					previous->next = next;					delete node;				}				//如果待删除的结点是头结点，直接删除该结点，并令next结点成为头结点				else				{					newHead = next;					delete node;				}				node = next;			}			//当前结点不是待删除结点，更新结点			else			{				previous = node;				node = next;			}		}		return newHead;    }};void print(ListNode* head){	if(!head)	{		cout << "no result" << endl;	}	ListNode* tempHead = head;	while(head)	{		cout << head->val << " ";		head = head->next;	}	cout << endl;	head = tempHead;}ListNode* buildList(vector<int>& nums){	if(nums.empty())	{		return NULL;	}	int size = nums.size();	ListNode* head ;	ListNode *tail;	ListNode* node;	for(int i = 0 ; i < size ; i++)	{		if(i)		{			node = new ListNode(nums.at(i));			tail->next = node;			tail = node;		}		else		{			head = new ListNode(nums.at(i));			tail = head;		}	}	return head;}void deleteList(ListNode* head){	ListNode* node;	while(head)	{		node = head->next;		delete head;		head = node;	}}void process(){	 vector<int> nums;	 int value;	 int num;	 Solution solution;	 vector<int> result;	 int delValue;	 while(cin >> num >> delValue )	 {		 nums.clear();		 for(int i = 0 ; i < num ; i++)		 {			 cin >> value;			 nums.push_back(value);		 }		 ListNode* head = buildList(nums);		 ListNode* newHead = solution.removeElements(head , delValue);		 print(newHead);		 deleteList(newHead);//删除节点了	 }}int main(int argc , char* argv[]){	process();	getchar();	return 0;}