71 lines
3.2 KiB
C++
71 lines
3.2 KiB
C++
//设计一个字符串类String，通过运算符重载实现字符串的输入、输出以及+=、==、!=、<、>、>=、[ ]等运算。
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#include <iostream>
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#include <cstring>
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using namespace std;
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class String {
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private:
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int length; //字符串长度
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char *sPtr; //存放字符串的指针
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void setString( const char *s2);
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friend ostream &operator<<(ostream &os, const String &s);
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friend istream &operator>>(istream &is, String &s); //重载输入运算符
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public:
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String( const char * = "" );
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const String &operator=(const String &R); //重载赋值运算符 =
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const String &operator+=(const String &R); //字符串的连接 +=
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bool operator==(const String &R); //字符串的相等比较 ==
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bool operator!=(const String &R); //字符串的不等比较 !=
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bool operator!() ; //判定字符串是否为空
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bool operator<(const String &R) const; //字符串的小于比较 <
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bool operator>(const String &R); //字符串的大于比较 >
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bool operator>=(const String &R); //字符串的大于等于比较
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char &operator[](int); //字符串的下标运算
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~String();
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};
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const String &String::operator+=(const String &R) {
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char *temp = sPtr;
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length += R.length;
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sPtr = new char[length+1];
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strcpy(sPtr,temp );
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strcat(sPtr,R.sPtr );
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delete [] temp;
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return *this;
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}
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bool String::operator==(const String &R){return strcmp(sPtr,R.sPtr)==0;}
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bool String::operator!=(const String & R){return !(*this==R);}
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bool String::operator!(){return length ==0;}
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bool String::operator<(const String &R)const{return strcmp(sPtr,R.sPtr)<0;}
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bool String::operator>(const String &R){return R<*this;}
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bool String::operator>=(const String &R){return !(*this<R);}
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char &String::operator[](int subscript){return sPtr[subscript];}
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int main(){
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String s1("happy"),s2("new year"),s3;
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cout << "s1 is " << s1 << "\ns2 is " << s2 << "\ns3 is " << s3
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<< "\n比较s2和s1:"
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<< "\ns2 ==s1结果是 " << ( s2 == s1 ? "true" : "false")
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<< "\ns2 != s1结果是 " << ( s2 != s1 ? "true" : "false")
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<< "\ns2 > s1结果是 " << ( s2 > s1 ? "true" : "false")
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<< "\ns2 < s1结果是 " << ( s2 < s1 ? "true" : "false")
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<< "\ns2 >= s1结果是 " << ( s2 >= s1 ? "true" : "false");
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cout << "\n\n测试s3是否为空: ";
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if (!s3){
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cout << "s3是空串"<<endl; //L3
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cout<<"把s1赋给s3的结果是：";
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s3 = s1;
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cout << "s3=" << s3 << "\n"; //L5
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}
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cout << "s1 += s2 的结果是：s1="; //L6
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s1 += s2;
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cout << s1; //L7
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cout << "\ns1 += to you 的结果是："; //L8
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s1 += " to you";
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cout << "s1 = " << s1 <<endl; //L9
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s1[0] = 'H';
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s1[6] = 'N';
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s1[10] = 'Y';
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cout << "s1 = " << s1 << "\n"; //L10
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system("pause");
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return 0;
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}
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