Reverse Linked List

4-4 Reverse Linked List   (20分)

Write a nonrecursive procedure to reverse a singly linked list in $O(N)$ time using constant extra space.

Format of functions:

List Reverse( List L );

where List is defined as the following:

typedef struct Node *PtrToNode;typedef PtrToNode List;typedef PtrToNode Position;struct Node {    ElementType Element;    Position Next;};

The function Reverse is supposed to return the reverse linked list of L, with a dummy header.

Sample program of judge:

#include <stdio.h>#include <stdlib.h>typedef int ElementType;typedef struct Node *PtrToNode;typedef PtrToNode List;typedef PtrToNode Position;struct Node {    ElementType Element;    Position Next;};List Read(); /* details omitted */void Print( List L ); /* details omitted */List Reverse( List L );int main(){    List L1, L2;    L1 = Read();    L2 = Reverse(L1);    Print(L1);    Print(L2);    return 0;}/* Your function will be put here */

Sample Input:

51 3 4 5 2

Sample Output:

2 5 4 3 1
2 5 4 3 1
//此题同时要把原链表翻转List Reverse( List L ){    List oldlist=L->Next;    List newlist;    newlist=(struct Node*)malloc(sizeof(struct Node));    newlist->Next=NULL;    while(oldlist){        struct Node* temp=oldlist->Next;        oldlist->Next=newlist->Next;        newlist->Next=oldlist;        oldlist=temp;    }    //翻转原链表    struct Node* tempnew=newlist->Next;    struct Node* tempold=L;    while(tempnew){        tempold->Next=tempnew;        tempold=tempold->Next;        tempnew=tempnew->Next;    }    tempold->Next=NULL;    return newlist;}