“串”学习——三种表示方法

串有三种表示方法：

str.h

#ifndef _STR_H
#define _STR_H
#define MAXSTRING 255

typedef unsigned char STR[MAXSTRING+1];


void NewStr(STR &s,char *str);

void ClearStr(STR &s);

int StrCompare(STR s,STR t);

int StrConcat(STR &s,STR t);

int SubStr(STR &s,STR t,int pos,int len);

#endif

str.cpp

#include<stdio.h>
#include<stdlib.h>
#include"str.h"

void NewStr(STR &s,char *str)
{
	int i;
	if(str == NULL)
		return;
	for(i=0; str[i]; i++)
		s[i] = str[i];
	s[i] = 0;
}


void ClearStr(STR &s)
{
	s[0] = 0;
}

int StrCompare(STR s,STR t)
{
	int i;
	for(i=0; s[i] && t[i] ;i++)
		if(s[i] != t[i])
			return s[i] - t[i];
	if(s[i])
		return 1;
	else if(t[i])
		return -1;
	else 
		return 0;
}

int StrConcat(STR &s,STR t)
{
	int i,j;
	for(i=0; s[i] ;i++);
	for(j=0; t[j] && i<= MAXSTRING ;i++,j++)
		s[i] = t[j];
	if(i>MAXSTRING && t[j])
	{
		ClearStr(s);
		return 0;
	}
	s[i] = 0;
}

int SubStr(STR &s,STR t,int pos,int len)
{
	int i,j;
	for(i=0; i<pos -1; i++)
		if(!t[i]) return 0;
	for(j=0; j<len && t[i] ;i++,j++)
		s[j] = t[i];
	if(j!=len)
	{
		ClearStr(s);
		return 0;
	}else{
		s[j] = 0;
		return 1;
	}
}

testString.cpp

#include<stdio.h>
#include "str.h"

void main()
{
	int res;
	STR t,s;
	NewStr(s,"hello");
	printf("s=%s\n",s);
	NewStr(t,"hello");
	res = StrCompare(s,t);
	if(res == 0)
		printf("s==t\n");
	else if(res > 0)
		printf("s > t\n");
	else 
		printf("s < t\n");
	NewStr(t," world");
	StrConcat(s,t);
	printf("s=%s\n",s);
	ClearStr(t);

	SubStr(t,s,2,6);
	printf("t=%s\n",t);
	ClearStr(s);
}

str.h

#ifndef _STR_H
#define _STR_H

typedef struct
{
	char *ch;
	int len;
}STR;


STR *NewStr(char *str);

void DestroyStr(STR *s);

void ClearStr(STR *s);

int StrCompare(STR *s,STR *t);

int StrConcat(STR *s,STR *t);

STR * SubStr(STR *s,int pos,int len);

#endif

str.c

#include<stdio.h>
#include<stdlib.h>
#include"str.h"

//根据char[]创建字符串
STR *NewStr(char *str)
{
	STR * s = NULL;
	int i;
	s = (STR *)malloc(sizeof(STR));
	if(s == NULL) return NULL;
	//循环到str[i]==\0时结束,i就是字符串的长度
	for(i = 0; str[i] ; ++i);
	s->ch = (char *)malloc((i + 1) * sizeof(char));
	if(s->ch == NULL)
	{
		free(s);
		return NULL;
	}
	//将str中内容搬到s.ch里
	s->len = i;
	while(i>=0)
	{
		s->ch[i] = str[i];
		--i;
	}
	return s;
}

void DestroyStr(STR *s)
{
	free(s->ch);
	free(s);
}

void ClearStr(STR *s)
{
	free(s->ch);
	s->ch = NULL;
	s->len = 0;
}

int StrCompare(STR *s,STR *t)
{
	int i;
	for(i = 0; i < s->len && i < t->len;i++)//abc abcde
		//s->ch[i]ASCII码大则返回正数代表大于关系
		//如果s->ch[i]比较小，则返回负数代表小于关系
		if(s->ch[i] != t->ch[i])
			return s->ch[i] - t->ch[i];
	//s比t短时返回负数，比t长时返回正，一样长返回0
	return s->len - t->len;
}

int StrConcat(STR *s,STR *t)
{
	//s,t都指向一块内存区，而他们合并后的内存区一定比他们大
	char *temp = NULL;
	int i;
	temp = (char *)malloc((s->len + t->len +1) * sizeof(char));
	if(temp == NULL) return 0;
	for(i = 0;i < s->len ;i++)
		temp[i] = s->ch[i];
	for(; i < s->len + t->len ;i++)
		temp[i] = t->ch[i - s->len];
	temp[i] = 0;
	ClearStr(s);
	s->ch = temp;
	s->len = i;
	return 1;
}

STR * SubStr(STR *s,int pos,int len)
{
	STR * t = NULL;
	if(pos < 1 || pos > s->len || len < 0 || len > s->len - pos)
		return NULL;
	t = NewStr("");
	ClearStr(t);
	t->ch = (char *)malloc((len + 1) * sizeof(char));
	if(t->ch == NULL) return NULL;
	t->len = len;
	//把有效的len位字符搬到t里面去
	for(--len ;len >= 0;-- len)
		t->ch[len] = s->ch[pos - 1 + len];
	t->ch[t->len] = 0;
	return t;
}

testString.c

#include<stdio.h>
#include "str.h"

void main()
{
	int res;
	STR *t = NULL,*s = NewStr("hello");
	printf("s=%s,len=%d\n",s->ch,s->len);
	t = NewStr("hello");
	res = StrCompare(s,t);
	if(res == 0)
		printf("s==t\n");
	else if(res > 0)
		printf("s > t\n");
	else 
		printf("s < t\n");
	t = NewStr(" world");
	StrConcat(s,t);
	printf("s=%s,len=%d\n",s->ch,s->len);
	DestroyStr(t);

	t = SubStr(s,2,5);
	printf("t=%s,len=%d\n",t->ch,t->len);
	DestroyStr(s);
}

str.h

#ifndef _STR_H
#define _STR_H
#define CHUNKSIZE 4

typedef struct Chunk
{
	char ch[CHUNKSIZE];
	struct Chunk *next;
}CHUNK;

typedef struct
{
	CHUNK *head,*tail;
	int curlen;
}STR;

STR *NewStr(char *str);

void DestroyStr(STR *s);

void ClearStr(STR *s);

int StrCompare(STR *s,STR *t);

int StrConcat(STR *s,STR *t);

STR * SubStr(STR *s,int pos,int len);

void PrintStr(STR *s);

#endif

str.c

#include<stdio.h>
#include<stdlib.h>
#include"str.h"

//根据char[]创建字符串
STR *NewStr(char *str)
{
	int i,j;
	CHUNK *temp;
	STR *s = (STR *)malloc(sizeof(STR));
	s->head = (CHUNK *)malloc(sizeof(CHUNK));
	s->tail = s->head;
	s->tail->next = NULL;
	s->curlen = 1;
	for(i=0,j=0; str[i] ;i++,j++){
		if(j == CHUNKSIZE){
			temp = (CHUNK *)malloc(sizeof(CHUNK));
			temp->next = NULL;
			s->tail->next = temp;
			s->tail = temp;
			s->curlen ++;
			j=0;
		}
		s->tail->ch[j] = str[i];
	}
	if(j == CHUNKSIZE)//有用的字符占满了最后一块空间
	{
		temp = (CHUNK *)malloc(sizeof(CHUNK));
		temp->next = NULL;
		s->tail->next = temp;
		s->tail = temp;
		s->curlen ++;
		j=0;
	}
	//填掉空白部分
	for(;j<CHUNKSIZE;j++)
		s->tail->ch[j] = 0;
	return s;
}

void DestroyStr(STR *s)
{
	CHUNK * temp = s->head;
	while(temp)
	{
		s->head = s->head->next;
		free(temp);
		temp = s->head;
	}
	free(s);
}

void ClearStr(STR *s)
{
	for(;s->head;s->head = s->head->next)
		free(s->head);
	s->head = s->tail = NULL;
	s->curlen = 0;
}

int StrCompare(STR *s,STR *t)
{
	int i;
	CHUNK *s1 = s->head,*t1 = t->head;
	for(i = 0; s1 && t1 ;i++)
	{
		if(s1->ch[i] != t1->ch[i])
			return s1->ch[i] - t1->ch[i];
		if(i == CHUNKSIZE-1)
		{
			s1 = s1->next;
			t1 = t1->next;
			i = -1;
		}
	}
	if(s1)
		return 1;
	else if(t1)
		return -1;
	else
		return 0;
}

int StrConcat(STR *s,STR *t)
{
	CHUNK * temp,*s1 = s->tail,*t1 = t->head;
	int i,j;
	for(i=0;s1->ch[i];i++);
	for(j=0;;i++,j++)
	{
		if(i == CHUNKSIZE){
			temp = (CHUNK *)malloc(sizeof(CHUNK));
			temp->next = NULL;
			s1->next = temp;
			s1 = temp;
			s->curlen ++;
			i=0;
		}
		if(j == CHUNKSIZE){
			t1 = t1->next;
			j=0;
		}
		if(t1->ch[j])
			s1->ch[i] = t1->ch[j];
		else
			break;
	}
	if(i == CHUNKSIZE)//有用的字符占满了最后一块空间
	{
		temp = (CHUNK *)malloc(sizeof(CHUNK));
		temp->next = NULL;
		s1->next = temp;
		s1 = temp;
		s->curlen ++;
		i=0;
	}
	//填掉空白部分
	for(;i<CHUNKSIZE;i++)
		s1->ch[i] = 0;
	return 1;
}

STR * SubStr(STR *s,int pos,int len)
{
	int i,j,k;
	CHUNK * s1 = s->head,*temp;
	STR * t = (STR *)malloc(sizeof(STR));
	t->head = (CHUNK *)malloc(sizeof(CHUNK));
	t->tail = t->head;
	t->tail->next = NULL;
	t->curlen = 1;
	for(i=0,j=0; s1 && i < pos - 1;i++,j++)
	{
		if(j == CHUNKSIZE - 1)
		{
			s1 = s1->next;
			j = -1;
		}
	}
	if(!s1)return 0;
	for(k = 0; s1 && i<pos - 1 + len ;i++,j++,k++)
	{
		if(k == CHUNKSIZE){
			temp = (CHUNK *)malloc(sizeof(CHUNK));
			temp->next = NULL;
			t->tail->next = temp;
			t->tail = temp;
			t->curlen ++;
			k=0;
		}

		t->tail->ch[k] = s1->ch[j];

		if(j == CHUNKSIZE - 1)
		{
			s1 = s1->next;
			j = -1;
		}
	}
	if(k == CHUNKSIZE)//有用的字符占满了最后一块空间
	{
		temp = (CHUNK *)malloc(sizeof(CHUNK));
		temp->next = NULL;
		t->tail->next = temp;
		t->tail = temp;
		t->curlen ++;
		k=0;
	}
	//填掉空白部分
	for(;k<CHUNKSIZE;k++)
		t->tail->ch[k] = 0;
	return t;
}

void PrintStr(STR *s)
{
	int i;
	CHUNK * temp = s->head;
	for(i=0; temp ;i++)
	{
		if(temp->ch[i])
			printf("%c",temp->ch[i]);
		else
			break;
		if(i == CHUNKSIZE - 1)
		{
			temp = temp->next;
			i = -1;
		}
	}
	printf("\n");
}

testString.c

#include<stdio.h>
#include "str.h"

void main()
{
	int res;
	STR *t = NULL,*s = NewStr("hello");
	PrintStr(s);
	t = NewStr("hello");
	res = StrCompare(s,t);
	if(res == 0)
		printf("s==t\n");
	else if(res > 0)
		printf("s > t\n");
	else 
		printf("s < t\n");
	t = NewStr(" world");
	StrConcat(s,t);
	PrintStr(s);
	DestroyStr(t);

	t = SubStr(s,2,6);
	PrintStr(t);
	DestroyStr(s);
}