C++ 程序1-9

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#include <iostream>
#include <string>

using namespace std;

int main()
{

    string str="1234";
    if(str.empty())
        cout << "str is NULL" << ".length="<< str.length() << endl;
    else
        cout << "str is not NULL" <<".length="<< str.length()<< endl;

    str= str.append("abcdefg");

if(str.empty())
        cout << "str is NULL" << ".length="<< str.length() << endl;
    else
        cout << "str is not NULL" <<".length="<< str.length()<< endl;





  cout<< "str is " << str << ",size=" <<str.size()<< endl;
   const char *p = str.c_str();//把C_str字符串给P指针

   cout << "p="<< p <<endl;
   cout <<"find:"<< str.find("cd",0)<<endl;
   cout <<"find:"<< str.find("cd",12)<<endl;
   string strl = str.insert(4,"ABC");
   cout << strl << endl;


    return 0;
}