string
construct with no arguments, e.g., string str1, str2;
member functions include:
<![CDATA[
int length(); // returns number of chars in string
int find(string substring, int startpos = 0);
// returns position of first occurrence of
// substring, starting at startpos
int find(char ch, int startpos = 0);
// similarly finds a character
string substr(int startpos, int size);
// returns substring starting at startpos,
// of length size
void insert(int startpos, string substring);
// inserts substring at startpos position
void remove(int startpos, int size);
// removes substring starting at startpos,
// of length size
char * c_str(); // returns equivalent C-style string
]]>
operators include:
<![CDATA[
[] // indexing (note: first char at index 0)
+ // concatenation
= // assignment
== != < <= > >= // relational operators
]]>
vector
templated, construct with one argument, the vector size e.g., vector<int> nums(100);
member functions include:
<![CDATA[
int length(); // returns size of vector
void resize(int newsize); // resizes the vector to newsize,
// copying any old entries
void push_back(const <TYPE> & item);
// adds item to end of vector
void pop_back(); // removes item at end of vector
<TYPE> & back(); // returns item at end of vector
]]>
operators include:
<![CDATA[
[] // indexing (note: first item at index 0)
= // assignment
]]>
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<![CDATA[
// Demonstration program to show the use of strings and vectors.
//
// The program reads in strings and displays statistics, including the
// total number of words, total number of unique words, and longest and
// shortest word lengths. It terminates on the END-OF-INPUT character
// (^Z for Windows, ^D for UNIX).
//
// Author: Dave Reed
///////////////////////////////////////////////////////////////////////
#include <iostream> // NEEDED for cin, cout
#include <string> // NEEDED for string
#include <vector> // NEEDED for vector
using namespace std;
int main()
{
int totalWords = 0;
int longest = 0, shortest = 10000; // ASSUMES NO STRING > 10000 CHARS
vector<string> unique; // CREATES DEFAULT VECTOR, SIZE 0
string str; // READ STRINGS (DELIMITED BY
while (cin >> str) { // WHITESPACE) UNTIL ^Z
totalWords++; // UPDATE TOTAL # OF WORDS
if (str.length() > longest) { // UPDATE LONGEST WORD IF NEC.
longest = str.length();
}
if (str.length() < shortest) { // UPDATE SHORTEST WORD IF NEC.
shortest = str.length();
}
bool found = false; // SEARCH FOR WORD IN
for (int i = 0; i < unique.size(); i++) { // VECTOR OF UNIQUE WORDS
if (unique[i] == str) { // SO FAR.
found = true; // SET FLAG AND EXIT LOOP
break; // IF FOUND.
}
}
if (!found) { // IF NOT FOUND,
unique.push_back(str); // ADD TO END OF VECTOR
}
}
cout << "Total number of words = " << totalWords << endl;
cout << "Number of unique words = " << unique.size() << endl;
if (totalWords > 0) {
cout << "The shortest word was length " << shortest << endl;
cout << "The longest word was length " << longest << endl;
}
return 0;
}
]]>
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Other useful libraries
fstream
ifstream and ofstream class definitions for reading/writing files
construct with one argument, a C-style string, e.g.,
<![CDATA[
ifstream instr("foo.in"); cin << filename;
ofstream outstr(filename.c_str());
]]>
can read from/write to files streams just like standard streams
<![CDATA[
instr >> x; outstr << "Howdy" << endl;
]]>
strstream
istrstream class definition for reading info from strings
(useful for processing line-oriented text)
construct with one argument, a C-style string, e.g.,
<![CDATA[
istrstream instr("a b c");
]]>
can read from string streams just like standard streams
<![CDATA[
while (instr >> letter) {
cout << letter << endl;
}
]]>
cctype
routines for manipulating and testing characters
<![CDATA[
bool isalpha(ch) returns true if ch is alphanumeric
bool isupper(ch) returns true if ch is an upper case letter ('A'..'Z')
bool islower(ch) returns true if ch is a lower case letter ('a'..'z')
bool isdigit(ch) returns true if ch is a digit ('0'..'9')
bool isspace(ch) returns true if ch is whitespace (space, tab, CR)
bool isspunct(ch) returns true if ch is a punctuation mark
char toupper(ch) returns upper case version of ch (or just ch if not a letter)
char tolower(ch) returns lower case version of ch (or just ch if not a letter)
]]>
iomanip
routines for manipulating I/O display
<![CDATA[
setprecision(N) sets flags so that next value displayed (if real) will have N
digits to the right of the decimal place
setiosflags(ios::fixed) sets flags so that real values are displayed with a
fixed number of digits (as set by setprecision)
]]>
|
<![CDATA[
// Demonstration program to show the use of input string streams to
// read and process line-oriented data, and also the use of
// setprecision and setiosflags to control the display of real values.
//
// The program reads in lines of integers and displays the average of
// the integers on each line. It terminates when the input line
// contains only the word "DONE".
//
// Author: Dave Reed
///////////////////////////////////////////////////////////////////////
#include <iostream> // NEEDED FOR cin
#include <iomanip> // NEEDED FOR setprecision
#include <string> // NEEDED for string
#include <strstream> // NEEDED for istrstream
using namespace std;
int main()
{
string str; // CAN READ ENTIRE LINE OF TEXT
getline(cin, str); // INTO A STRING (EATS EOL CHAR)
while (str != "DONE") {
istrstream istr(str.c_str()); // CREATE INPUT STRING STREAM TO
// HOLD STRING CONTENTS (NOTE:
// MUST CONVERT C++ STRING INTO
// C-STYLE STRING)
int num, count = 0;
double sum = 0;
while (istr >> num) { // CAN READ FROM INPUT STRING
sum += num; // JUST LIKE ANY OTHER STREAM
count++;
}
// CAN SET THE PRECISION (NUM
// DIGITS TO RIGHT OF DECIMAL
// PLACE) FOR REAL VALUES
if (count == 0) {
cout << "There were no numbers to average." << endl;
}
else {
cout << "The average of the " << count << " numbers is "
<< setprecision(3) << setiosflags(ios::fixed)
<< sum/count << endl;
}
getline(cin, str);
}
return 0;
}
]]>
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