串和模式匹配

const String& s) const;
int operator!= (char *s) const;
friend int operator!= (char *str, const String& s);
int operator< (const String& s) const;
String& String::operator= (char *s) { int slen = strlen(s) + 1;
// if sizes differ, delete current string and reallocate
if (slen != size) { delete [] str; str = new char [slen]; if (str == NULL) Error(outOfMemory); size = slen; } strcpy(str,s); return *this;
电子系1999级
数据结构
Data Structure With C or C++
串
串---由字符组成的线性表，也叫 字符串 串是非数值计算算法处理的主要 对象 在模式匹配，程序编译，数据处 理等领域有广泛的应用
串类型的定义
串类型的实现 串的模式匹配
串类型的定义
1。用数组定义串 #define MAXSTRLEN 255 typedef unsigned SString[MAXSTRLEN+1];
int operator== (char *str, const String& s) { return strcmp(str,s.str) == 0; }
// String != String
int String::operator!= (const String& s) const { return strcmp(str,s.str) != 0; }
// String < String
int String::operator< (const String& s) const { return strcmp(str,s.str) < 0; }
// String < C++String
int String::operator< (char *s) const { return strcmp(str,s) < 0; }
// String I/O
friend ostream& operator<< (ostream& ostr,
const String& s); friend istream& operator>> (istream& istr, String& s); int ReadString(istream& is=cin, char delimiter='\n'); int Length(void) const;
// allocate same amount of space as s uses. copy string
str = new char [size]; if (str == NULL) Error(outOfMemory); strcpy(str, s.str); }
// destructor
String& operator= (const String& s); String& operator= (char *s); int operator== (const String& s) const; int operator== (char *s) const;
friend int operator== (char *str, const String& s);
if (str == NULL) Error(outOfMemory); strcpy(str,s); }
// copy constructor String::String(const String& s) {
// current object as length of s
size = s.size;
堆分配存储串类的实现//“strclass.h” #ifndef STRING_CLASS
#define STRING_CLASS
#include <iostream.h> #include <string.h>
#include <stdlib.h>
#ifndef NULL
const int NULL = 0;
// String != C++String
int String::operator!= (char *s) const { return strcmp(str,s) != 0; }
// C++String != String
int operator!= (char *str, const String& s) { return strcmp(str,s.str) != 0; }
String::~String(void) { delete [] str; }
// assignment operator. String to String
String& String::operator= (const String& s) { if (s.size != size) { delete [] str; str = new char [s.size]; if(str == NULL) Error(outOfMemory);
// String <= C++String
int String::operator<= (char *s) const { return strcmp(str,s) <= 0; }
// C++String <= String
int operator<= (char *str, const String& s) { return strcmp(str,s.str) <= 0; }
Sstring s1, s2; //用s1[0], s2[0]存储各自的长度
2。堆分配存储表示
typedef struct{ char *ch; int length; }HString;
HString s; s.length=15; s.ch=new char[s.length];
3.块链存储
#define CHUNKSIZE 80 typedef struct Chunk{ char ch[CHUNKSIZE]; Chunk *next; }； typedef struct{ Chunk *head,*tail; int curlen; }LString; //定长字符串作元素的线性链表
int operator< (char *s) const;
friend int operator< (char *str, const String& s);
int operator<= (const String& s) const; int operator<= (char *s) const;
int operator>= (const String& s) const;
int operator>= (char *s) const;
friend int operator>= (char *str, const String& s);
String operator+ (const String& s) const; String operator+ (char *s) const;
// C++String < String
int operator< (char *str, const String& s) { return strcmp(str,s.str) < 0; }
// String <= String
int String::operator<= (const String& s) const { return strcmp(str,s.str) <= 0; }
#endif // NULL const int outOfMemory = 0, indexError = 1;
class String
{ char *str; int size;
void Error(int errorType, int badIndex = 0) const;
public: String(char *s = “ ” ); String(const String& s); ~String(void);
// constructor. allocate memory and copy in a C++String
String::String(char *s) { size = strlen(s) + 1; str = new char [size];
// terminate program if memory is exhausted.
// String == C++String
int String::operator== (char *s) const { return strcmp(str,s) == 0; }