C++ Tutorial/Data Types/Your Set

A set class for characters

<source lang="cpp">/* Quote from: C++: A Beginner"s Guide, Second Edition

1. Publisher: McGraw-Hill Osborne Media; 2 edition (December 3, 2003)
2. Language: English
3. ISBN-10: 0072232153
4. ISBN-13: 978-0072232158

• /

1. include <iostream>

using namespace std;

const int MaxSize = 100;

class Set {

 int len; // number of members  
 char members[MaxSize]; // this array holds the set     

 /* The find() function is private because it  
    is not used outside the Set class. */  
 int find(char ch); // find an element 

public:

 // Construct a null set.  
 Set() { len = 0; }  
 
 // Return the number of elements in the set. 
 int getLength() { return len; }  

 void showset(); // display the set 
 bool isMember(char ch);  // check for membership 

 Set operator +(char ch); // add an element   
 Set operator -(char ch); // remove an element 

 Set operator +(Set ob2); // set union 
 Set operator -(Set ob2); // set difference   

};

/* Return the index of the element

  specified by ch, or -1 if not found. */ 

int Set::find(char ch) {

 int i;  
     
 for(i=0; i < len; i++)  
   if(members[i] == ch) return i;  
 
 return -1;  

}

// Show the set. void Set::showset() {

 cout << "{ "; 
 for(int i=0; i<len; i++) 
   cout << members[i] << " "; 

 cout << "}\n"; 

}

/* Return true if ch is a member of the set.

  Return false otherwise. */ 

bool Set::isMember(char ch) {

 if(find(ch) != -1) return true; 
 return false; 

}

// Add a unique element to a set. Set Set::operator +(char ch) {

 Set newset; 

 if(len == MaxSize) { 
   cout << "Set is full.\n"; 
   return *this; // return existing set 
 } 

 newset = *this; // duplicate the existing set 
    
 // see if element already exists  
 if(find(ch) == -1) { // if not found, then add  
   // add new element to new set  
   newset.members[newset.len] = ch;  
   newset.len++;  
 }  
 return newset; // return updated set  

}

// Remove an element from the set. Set Set::operator -(char ch) {

 Set newset; 
 int i = find(ch); // i will be -1 if element not found  
 
 // copy and compress the remaining elements  
 for(int j=0; j < len; j++)  
   if(j != i) newset = newset + members[j];  
 
 return newset;  

}

// Set union. Set Set::operator +(Set ob2) {

 Set newset = *this; // copy the first set  
 
 // Add unique elements from second set. 
 for(int i=0; i < ob2.len; i++)   
   newset = newset + ob2.members[i];  
 
 return newset; // return updated set  

}

// Set difference. Set Set::operator -(Set ob2) {

 Set newset = *this; // copy the first set  
 
 // Subtract elements from second set.  
 for(int i=0; i < ob2.len; i++)   
   newset = newset - ob2.members[i];  
 
 return newset; // return updated set  

}

// Demonstrate the Set class. int main() {

 // construct 10-element empty Set    
 Set s1;     
 Set s2; 
 Set s3; 
 
 s1 = s1 + "A";  
 s1 = s1 + "B";  
 s1 = s1 + "C";  
 
 cout << "s1 after adding A B C: ";   
 s1.showset(); 

 cout << "\n"; 

 cout << "Testing for membership using isMember().\n";  
 if(s1.isMember("B")) 
   cout << "B is a member of s1.\n"; 
 else 
   cout << "B is not a member of s1.\n"; 

 if(s1.isMember("T")) 
   cout << "T is a member of s1.\n"; 
 else 
   cout << "T is not a member of s1.\n"; 

 cout << "\n"; 

 s1 = s1 - "B";  
 cout << "s1 after s1 = s1 - "B": ";   
 s1.showset(); 
 
 s1 = s1 - "A";  
 cout << "s1 after s1 = s1 - "A": ";   
 s1.showset(); 
 
 s1 = s1 - "C";  
 cout << "s1 after a1 = s1 - "C": ";   
 s1.showset(); 

 cout << "\n"; 

 s1 = s1 + "A";  
 s1 = s1 + "B";  
 s1 = s1 + "C";  
 cout << "s1 after adding A B C: ";   
 s1.showset(); 
 
 cout << "\n"; 

 s2 = s2 + "A";  
 s2 = s2 + "X";  
 s2 = s2 + "W";  
 
 cout << "s2 after adding A X W: ";   
 s2.showset(); 
 
 cout << "\n"; 

 s3 = s1 + s2;  
 cout << "s3 after s3 = s1 + s2: ";   
 s3.showset(); 
 
 s3 = s3 - s1;  
 cout << "s3 after s3 - s1: ";   
 s3.showset(); 
 
 cout << "\n"; 

 cout << "s2 after s2 = s2 - s2: ";   
 s2 = s2 - s2;  // clear s2  
 s2.showset(); 
 
 cout << "\n"; 

 s2 = s2 + "C"; // add ABC in reverse order  
 s2 = s2 + "B";  
 s2 = s2 + "A";  

 cout << "s2 after adding C B A: ";   
 s2.showset(); 
 
 return 0; 

}</source>

s1 after adding A B C: { A B C }
Testing for membership using isMember().
B is a member of s1.
T is not a member of s1.
s1 after s1 = s1 - "B": { A C }
s1 after s1 = s1 - "A": { C }
s1 after a1 = s1 - "C": { }
s1 after adding A B C: { A B C }
s2 after adding A X W: { A X W }
s3 after s3 = s1 + s2: { A B C X W }
s3 after s3 - s1: { X W }
s2 after s2 = s2 - s2: { }
s2 after adding C B A: { C B A }