c++ string

C++ string class

The C++ Standard Template Library (STL) contains a string class that is used in several computer science classes. In order to use the string class you should include the following statements:
#include <string>
using std::string;

The following examples assume these declarations and initial values for each:

string s = "abc def abc";
string s2 = "abcde uvwxyz";
char c;
char ch[] = "aba daba do";
char *cp = ch;
unsigned int i;

Stream input	cin >> s;	Changes the value of s to the value read in. The value stops at whitespace.
Stream output	cout << s;	Writes the string to the specified output stream.
Line input	getline(cin, s);	Reads everything up to the next newline character and puts the result into the specified string variable.
Assignment	s = s2;s = "abc"; s = ch; s = cp;	A string literal or a string variable or a character array can be assigned to a string variable. The last two assignments have the same effect.
Subscript	s[1] = 'c'; c = s[1];	Changes s to equal "acc def abc" Sets c to 'b'. The subscript operator returns a char value, not a string value.
Length	i = s.length(); i = s.size();	Either example sets i to the current length of the string s
Empty?	if(s.empty()) i++; if(s == "") i++;	Both examples add 1 to i if string s is now empty
Relational operators	if (s < s2) i++;	Uses ASCII code to determine which string is smaller. Here the condition is true because a space comes before letter d
Concatenation	s2 = s2 + "x"; s2 += "x";	Both examples add x to the end of s2
Substring	s = s2.substr(1,4); s = s2.substr(1,50);	The first example starts in position 1 of s2 and takes 4 characters, setting s to "bcde". In the second example, s is set to "bcde uvwxyz". If the length specified is longer than the remaining number of characters, the rest of the string is used. The first position in a string is position 0.
Substring replace	s.replace(4,3,"x");	Replaces the three characters of s beginning in position 4 with the character x. Variable s is set to "abc x abc".
Substring removal	s.erase(4,5); s.erase(4);	Removes the five characters starting in position 4 of s. The new value of s is "abc bc". Remove from position 4 to end of string. The new value of s is "abc ".
Character array to string	s = ch;	Converts character array ch into string s.
String to character array	cp = s.c_str();	Pointer cp points to a character array with the same characters as s.
Pattern matching	i = s.find("ab",4); if(s.rfind("ab",4) != string::npos)    cout << "Yes" << endl;	The first example returns the position of the substring "ab" starting the search in position 4. Sets i to 8. The find and rfind functions return the unsigned int string::npos if substring not found. The second example searches from right to left starting at position 4. Since the substring is found, the word Yes is printed.