C++string的操作

 #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;

 }