头文件
typedef struct{
char *ch;
int length;
}HString;
#define MAXSTRLEN 255
#define OK 1
#include<stdlib.h>
#include<string>
#define TRUE 1
#define FALSE 0
#define ERROR 0
#define OVERFLOW -2
#include<iostream>
using namespace std;
typedef int Status;
Status StrAssign(HString &T,char *chars);
Status SubString(HString &Sub,HString S,int pos,int len);
Status Concat(HString &T,HString S1,HString S2);
Status StrPrint(HString S);
void InitalStr(HString &T);
函数
#include "com.h"
//初始化一个串
void InitalStr(HString &T){
T.ch = NULL;
T.length = 0;
}
Status Concat(HString &T,HString S1,HString S2){
int i;
if(T.ch)
free(T.ch);
if(!(T.ch=(char*)malloc((S1.length+S2.length)*sizeof(char))))
exit(OVERFLOW);
for(i=0;i<S1.length;i++)
T.ch[i]=S1.ch[i]; //不存在截断,于是直接将S1赋给T
T.length=S1.length+S2.length; //T的长度为S1和S2相加
for(i=0;i<S2.length;i++) //将S2赋给T
T.ch[S1.length+i]=S2.ch[i];
return OK;
}
//返回串S的第pos个字符起长度为len的子串
Status SubString(HString &Sub,HString S,int pos,int len){
int i;
if(pos<1||pos>S.length||len<0||len>S.length-pos+1)
return ERROR;
if(Sub.ch) free(Sub.ch);
if(!len) //长度为0,就全部置为0
{
Sub.ch=NULL;
Sub.length=0;
}
else{
Sub.ch=(char *)malloc(len*sizeof(char)); //分配空间
if(!Sub.ch) exit(OVERFLOW);
for(i=0;i<len;i++)
Sub.ch[i]=S.ch[pos-1+i]; //将串S的第pos个字符起长度为len的子串赋给Sub
Sub.length= len; //设置Sub的长度
}
return OK;
}
Status StrAssign(HString &T,char *chars){
int i;
char *c;
if(T.ch) free(T.ch);
for(i=0,c=chars; *c ;++i,++c); //求chars长度i
if(!i){
T.ch = NULL; //串常量chars长度为0时串为空串长度0存储区间指向NULL
T.length = 0;
}
else{
if(!(T.ch=(char*)malloc(i*sizeof(char))))
exit(OVERFLOW);
for(int j = 0; j < i; j++)
T.ch[j] = chars[j]; //写入chars串
T.length = i;
}
return OK;
}
//输出函数
Status StrPrint(HString S)
{
int i;
for (i = 0; i < S.length; i++)
{
cout << S.ch[i];
}
cout << endl;
return 0;
}
主函数
#include "com.h"
int main(){
int ch;
int q=1,len,pos;
char a[MAXSTRLEN],b[MAXSTRLEN];
HString S1,S2,T,Sub;
InitalStr(T);
InitalStr(S1);
InitalStr(S2);
InitalStr(Sub);
cout << "请输入主串S1" << endl;
cin >> a ;
StrAssign(S1, a);
cout<<endl;
while(q){
cout<<endl;
cout<<"*********************"<<endl;
cout<<"1.连接串S1和S2"<<endl<<endl;
cout<<"2.返回串S1第pos个字符起长度为len的子串"<<endl<<endl;
cout<<"请输入选择:"<<endl;
cin>>ch;
switch(ch){
case 1:
cout << "请输入要和主串S1连接的S2" << endl;
cin >> b;
StrAssign(S2, b);
if (Concat(T,S1,S2))
{
cout<<"连接成功后串为:";
StrPrint(T);
}
else
cout << "串连接失败" << endl;
break;
case 2:
cout << "请输入求子串的pos和len的值"<<endl;
cin >> pos>> len;
if (SubString(Sub,S1,pos,len))
{
cout << "输出子串Sub:";
StrPrint(Sub);
}
else
cout << "求子串失败!" << endl;
break;
default:q=0; break;
}
} return 0;
}
结果