[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_INCLUDED

struct Node;
typedef struct Node *PtrToNode;
//  List and Position are pointers
typedef 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 yet
ElementType Retrive(Position P);//not implemented yet
void 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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