#include <iostream>

 using namespace std;

 int main()

 {

     //initilization

     string            str("abc.ddd");

     const    string     cstr("fff.ccc");

     string substr1(str, ); //c.ddd

     string substr2(str, , ); //c.d

     string substr3("abcdefg", ); //ab

     cout << "the value of substr1 is: " << substr1 << endl;

     cout << "the value of substr2 is: " << substr2 << endl;

     cout << "the value of substr3 is: " << substr3 << endl;

     //compare

     if(str > cstr)

         cout << "abc.ddd is larger than fff.ccc." << endl;

     else

         cout << "abc.ddd is less than fff.ccc." << endl;

     if(str.compare(cstr) > )

         cout << "abc.ddd is larger than fff.ccc." << endl;

     else

         cout << "abc.ddd is less than fff.ccc." << endl;

     //assign

     str = "sadfasdf";

     str.assign("a",); //a,\0,\0,\0,\0

     str.assign(,'a'); //a, a, a, a, a

     cout << "the value of str is: " << str << endl; //aaaaa

     //append

     str.append("bcd");

     cout << "the value of s after append is: " << str << endl; //aaaaabcd

     //insert

     //s.insert(1, 'd'); NOK!

     str.insert(, "ddd"); //adddaaaabcd

     cout << "the value of s after append is: " << str << endl;

     //find

     string::size_type idx = str.find(".");

     cout << "the index of . is: " << idx << endl; //3

     //substring

     string basestr = str.substr(, idx); //abc

     string extestr = str.substr(idx + , string::npos); //ddd

     cout << "the substr of str.substr(0, idx) is: " << basestr << endl;

     cout << "the substr of str.substr(idx, string::npos) is: " << extestr << endl;

     //compare

     if(extestr == "ddd")

         cout << "ddd file is found!" << endl;

     else

         cout << "ddd file is not found!" << endl;

     //replace

     string tmpname(str.replace(idx + , string::npos, "xxx")); //abc.xxx

     cout << "the string after replace extention is: " << tmpname << endl;

     //erase

     str = "internal";

     str.replace(,,"ex"); //external

     str.erase();

     str.erase(,);

     cout << "the string after erase is: " << str << endl;

     //clear

     str.clear();

     cout << "the string after clear is: " << str << endl;

     if(str.empty())

         cout << "the string is empty." << endl;

     else

         cout << "the string is not empty." << endl;

     if(str.begin() == str.end())

         cout << "equal." << endl;

     else

         cout << "unequal" << endl;

     //reverse

     str = "abcd";

     reverse(str.begin(), str.end());

     cout << "the string after reverse is: " << str << endl;

     str.assign(str.rbegin(), str.rend());

     cout << "the string after reverse is: " << str << endl;

     //data

     const char* pa = str.data();

     //size(), length()

     cout << "the size of str is: " << str.size() << endl;

     cout << "the size of str is: " << str.length() << endl;

     //[], at()

     char& r = str[];

     char* p = &str[];

     cout << "the 3rd char of str is: " << r << endl;

     cout << "the 4rd char of str is: " << *p << endl;

     str = "new value";

     //reference is invalid after str is re-assigned

     r = 'X';

     cout << "The value of str is: " << str << endl;

     //advanced find

     //Input: I was a deer

     //Output: reed a saw I

     const string delims(" \t,.;");

     string line;

     cout << "Please input a sentence: " << endl;

     getline(cin, line,'\n');

     cout << "The input sentence is: " << line << endl;

     //while find a word

     string::size_type begIdx, endIdx;

     begIdx = line.find_first_not_of(delims);

     while(begIdx != string::npos){

         endIdx = line.find_first_of(delims, begIdx);

         if(endIdx == string::npos);

             //endIdx = line.length();

         for(int i = endIdx - ; i >= static_cast<int>(begIdx); --i)

             cout << line[i];

         cout << ' ';

         begIdx = line.find_first_not_of(delims, endIdx);

     }

     cout << endl;

 }