第8周项目4 String类的构造

来源：互联网发布：宁家骏指出要用大数据编辑：程序博客网时间：2024/06/05 10:24
#include <iostream>#include <cstring>using namespace std;class String{public:    String();//默认构造函数    String(char *s);    String (String &s);    ~String();//析构函数    void display();    friend String operator+(String &s1,String &s2);    friend String operator-(String &s1,String &s2);private:    char *p;   //指向存储的字符串    int len;   //记录字符串的长度};String::String(){    len=0;    p=NULL;}String::String(char *s){    len=strlen(s);    p=new char[len+1];    strcpy(p,s);}String::String(String &s){    len=s.len;    if(p!=NULL) delete []p;   //当发生在赋值等情形时，原对象可能已经存在，需释放原有空间 ;    p=new char[len+1];    strcpy(p,s.p);}String::~String(){    if(!p)        delete[]p;}void String::display(){    cout<<p<<endl;}String operator+(String &s1,String &s2){    String s;    s.len=s1.len+s2.len;    s.p=new char[s.len+1];    strcpy(s.p,s1.p);    strcat(s.p,s2.p);    return s;}String operator-(String &s1,String &s2){    char *c1;//c1为截去尾部空格的字符串    c1=new char[s1.len+1];    strcpy(c1,s1.p);    int i=s1.len-1;    while(i>=0&&c1[i]==' ')        i--;    c1[i+1]='\0';    char *c2; //c2为去除前导空格的字符串    c2=new char[s2.len+1];    strcpy(c2,s2.p);    i=0;    while(i<s2.len&&c2[i]==' ')        ++i;    int j;    for(j=0;i<s2.len&&c2[i]!='\0';i++,j++)        c2[j]=c2[i];    c2[j]='\0';    String s;    s.len = strlen(c1)+strlen(c2);    s.p = new char[s.len+1];    strcpy(s.p,c1);    strcat(s.p,c2);    delete c1;    delete c2;    return s;}int main( ){    String string1("Hello "), string2(" World");    string1.display();    string2.display();    String string3;    string3 = string1 + string2;    string3.display();    string3 = string1 - string2;    string3.display();    return 0;}
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