45. 定义一个字符串类String,用来存放不定长的字符串,重载运算符,用于两个 字符串的大于的比较运算。#includestringusing std:string;class Stringprivate:char *p;public:String()p = NULL;String(char *pp)p = pp;friend bool operator =(String &a,String &b);friend bool operator (String &a, String &friend bool operator void display()std:cout if (strcmp(a.p, b.p) 0)bool operator if (strcmp(a.p, b.p) (a, b)a.display(); ;b.display();else if (operator =void main()String string(abc);String string1(abcscompare(string,string1);system(pause