[数据结构与算法分析] 单链表基本操作的实现

　　这几天还在啃Weiss书的Ch.3，随手把书上单链表基本操作的代码打了一遍，顺便补充了一点自己写的东西（一堆注释以及几个函数），经过测试应该是没问题。

　　这次尝试用所谓的"Google Style"写代码，习惯了缩进4空格的Windows风格后再改到缩进2空格，真的是有些不习惯。本来Google Style中，变量应该都是小写字母，但我实在不喜欢小写的L和P，变量命名仍就坚持自己的习惯——单字母变量大写，多字母小写。

　　需要注意的一些地方：

　　1，在几个函数中出现了类似while (P != NULL && P->Element != X) 这样子的代码，根据逻辑运算符的短路规则，如果P != NULL(链表末尾结点)，就不会再检查后面的布尔表达式。

　　2，原书使用  Position tmp = malloc(sizeof(struct Node)) 这样的代码，但根据Google Style 建议，改为" malloc(sizeof(tmp))"有利于保持同步（鉴于tmp的数据类型有可能改变）。

　　Code is here~

　　.h头文件：

#ifndef LINKLIST_H_INCLUDED#define LINKLIST_H_INCLUDEDstruct Node;typedef struct Node *PtrToNode;//  List and Position are pointerstypedef PtrToNode List;typedef PtrToNode Position;#define ElementType int//set the type of element as Integer//  Functions:List MakeEmpty(List L);List InitialList();int IsEmpty(List L);int IsLast(Position P, List L);Position Find(ElementType X, List L);void Delete(ElementType X, List L);Position FindPrevious(ElementType X, List L);void Insert(ElementType X, List L, Position P);void DeleteList(List L);Position Header(List L);Position First(List L);Position Last(List L);Position Advance(Position P);//not implemented yetElementType Retrive(Position P);//not implemented yetvoid PrintElement(Position P);void PrintList(List L);int SizeOfList(List L);int FindIndex(ElementType X, List L);int InsertAsTail(ElementType X, List L);int InsertAsHead(ElementType X, List L);#endif // LINKLIST_H_INCLUDED

　　

　　.c文件：

#include "LinkList.h"#include<stdio.h>#include<stdlib.h>struct Node {  ElementType Element;  Position Next;};List MakeEmpty(List L) {  //used for initialization  Position P = Header(L);  P->Next = NULL;  P->Element = 0;}List InitialList() {//return a new List (header)  List tmp;  tmp = malloc(sizeof(tmp));//standard malloc way for "tmp"  tmp->Next = NULL;  //  tmp = MakeEmpty(tmp);  return tmp;}int IsEmpty(List L) {//Return true if L is empty  return L->Next == NULL;}int IsLast(Position P, List L) {//Return true if P is the last position of the list L  return P->Next == NULL;}Position Header(List L) {  Position P = L;}Position First(List L) {  Position P = L->Next;}Position Last(List L) {  Position P = Header(L);  while (!IsLast(P,L)) {    P = P->Next;  }  return P;}Position Find(ElementType X, List L) {//  Return Position of X in L;NULL if not found;  Position P = L->Next;  while (P != NULL && P->Element != X)    //  You should first know if P is NULL, here we use shortcut "&&"    P = P->Next;  return P;}int FindIndex(ElementType X, List L) {  //Return Index of X in L;-1 if not found;Index starts from 1(not 0).  int index = 1;  Position P = L->Next;  while (P != NULL && P->Element != X) {    //  You should first know if P is NULL, here we use shortcut "&&"    P = P->Next;    index++;  }  return index; //header node is not counted in index}void Delete(ElementType X, List L) {//Delete the first occurrence of X in List L  Position P,tmp;  P = FindPrevious(X,L);  if (!IsLast(P,L)) {    tmp = P->Next;  //Now "tmp" is just which node you want to "delete" here    P->Next = tmp->Next;    free(tmp);  //the data at address tmp is meaningless after free it  }}Position FindPrevious(ElementType X, List L) {  //If X is not found, then Next Field of Returned Position is NULL  Position P = L;  while(P->Next != NULL && P->Next->Element != X)    P = P->Next;  return P; //If X not found in this List, P is the last node, P->Next is NULL}void Insert(ElementType X, List L, Position P) {//Insert After Position P  Position tmp = malloc(sizeof(tmp));  if (tmp == NULL) {    printf("Out of space!");  //  TODO(AllZY): Use a variable to indicate the state.  } else {    tmp->Element = X;    tmp->Next = P->Next;    P->Next = tmp;  //tmp should never be "NULL" when this line executed  }}int InsertAsTail(ElementType X, List L) {//  return index if inserted successfully, otherwise return -1//  Insert it after the last ele.  Position Tail = Last(L);  Position tmp = malloc(sizeof(tmp));  if (tmp == NULL) {    return -1;  } else {    tmp->Element = X;    tmp->Next = Tail->Next;    Tail->Next = tmp;  } //Is this what they called "google style"? I think it's a bit odd...}int InsertAsHead(ElementType X, List L) {//  return index if inserted successfully, otherwise return -1//  Insert it before the first ele.  Position Head = Header(L);  Position tmp = malloc(sizeof(tmp));  if (tmp == NULL) {    return -1;  } else {    tmp->Element = X;    tmp->Next = Head->Next;    Head->Next = tmp;  }}void DeleteList(List L) {  Position P,tmp;  P = L->Next;  L->Next = NULL;  while (P != NULL) {    tmp = P->Next;    free(P);    P = tmp;  }  /*  //an unreliable version, not recommended  while(P!=NULL)  {    free(P);    P = P->Next;  }  */}void PrintElement(Position P) {//Print one Element  ElementType e = P->Element;  printf("%d ",e);}void PrintList(List L) {//Print all elements in the List  Position P = First(L);  while (P != NULL) {    PrintElement(P);    P = P->Next;  }}int SizeOfList(List L) {  int count = 0;  Position P = First(L);  while (P != NULL) {    count++;    P = P->Next;  }  return count;}int main(){//  List L = malloc(sizeof (List));//  MakeEmpty(L);  List L = InitialList();  Position P = Header(L);  int i;  for (i = 1; i <= 10; i++) {    InsertAsTail(i,L);  }  for ( ; i <= 20; i++) {    InsertAsHead(i,L);  }  PrintList(L);  printf("\nSize of list is %d",SizeOfList(L));  Position p10 = Find(10,L);  printf("\nThe element in the Position of value \"10\" is %d\n",p10->Element);  printf("The index of Element 11 is %d\n",FindIndex(11,L));  DeleteList(L);  return 0;}

　　测试运行结果：

　　

 

参考资料：

《数据结构与算法分析》

http://google.github.io/styleguide/cppguide.html

http://zh-google-styleguide.readthedocs.org/en/latest/google-cpp-styleguide/

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