/*
*Ajanni Haltiwanger
*Comp 285/ 03A
*July 17, 2021
*Creating a Hash table to display a menu and its content
*/

#include <iostream>
#include <vector>
#include <fstream>

using namespace std;

class HashTable {
public:
    /* an array of 20 vectors of int type to hold the hash table for chaining */
    vector<int> ht_c[20];
    /* an array of int of size 20 to hold linear probing  hash table */
    int ht_l[20];
    
    /* default constructor to initialize each element of the array ht_l to 0 */
    HashTable() {
        for(int i=0; i < 20; i++)
            ht_l[i] = 0;
    }
    /* this function inserts the key into the vector which is at hash(key) position in the array of vectors ht_c */
    void putChaining(int key) {        
        ht_c[hash(key)].push_back(key);                
    }
    /* the idea is if the cell at array position hash(key) is occupied, it simply tries the next linear position which (hash(key) + 1) % 20 
     * we store the hash(key) in a temp variable and iterate till we find a vacant spot identified by 0 in the array. */
    void putLinear(int key) {
        int temp = hash(key);        
        if(ht_l[temp] != 0) {            
          while(ht_l[temp] != 0)
               temp = (temp + 1) % 20;                                        
        }
        ht_l[temp] = key;        
    }
    /* function to compute the hash value which is a simple key mod 20 function */
    int hash(int key) {
        return key % 20;
    }
    /* a function to the chaining hash table */
    void printChaining() {
        for(int i=0; i<20;i++) {
            cout << i << ": " ;
            for(int j=0; j<ht_c[i].size(); j++)
                cout << ht_c[i][j] << " ";
                cout << endl;
        }
        cout << endl;
        cout << endl;
    }
    /* a function to print the linear hash table */
    void printLinear() {
        for(int i=0; i<20;i++)
            cout << i << ": " << ht_l[i] << endl;
            cout << endl;
            cout << endl;
    }
};

int main(int argc, char *argv[]) {
    if(argc == 2) {
      HashTable ht = HashTable();   
      string file(argv[1]);
      ifstream reader(file);
      int key;
      while((reader >> key)) {            
            ht.putLinear(key);
            ht.putChaining(key);
      }
      int command = -1;
      while(command != 0) {
            cout << "1. Linear" <<endl;
            cout << "2. Chaining" <<endl;
            cout << "0. Exit" << endl;
            
            cin >> command;
            switch(command) {
                case 1 : ht.printLinear();break;
                case 2 : ht.printChaining();break;                
            }
        }
    }
    else {
       cout << "File name missing ... " << endl;
       return 0;
    }
}

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About C++

C++ is a widely used middle-level programming language.

  • Supports different platforms like Windows, various Linux flavours, MacOS etc
  • C++ supports OOPS concepts like Inheritance, Polymorphism, Encapsulation and Abstraction.
  • Case-sensitive
  • C++ is a compiler based language
  • C++ supports structured programming language
  • C++ provides alot of inbuilt functions and also supports dynamic memory allocation.
  • Like C, C++ also allows you to play with memory using Pointers.

Syntax help

Loops

1. If-Else:

When ever you want to perform a set of operations based on a condition If-Else is used.

if(conditional-expression) {
   //code
}
else {
   //code
}

You can also use if-else for nested Ifs and If-Else-If ladder when multiple conditions are to be performed on a single variable.

2. Switch:

Switch is an alternative to If-Else-If ladder.

switch(conditional-expression){    
case value1:    
 // code    
 break;  // optional  
case value2:    
 // code    
 break;  // optional  
......    
    
default:     
 code to be executed when all the above cases are not matched;    
}

3. For:

For loop is used to iterate a set of statements based on a condition.

for(Initialization; Condition; Increment/decrement){  
  //code  
}

4. While:

While is also used to iterate a set of statements based on a condition. Usually while is preferred when number of iterations are not known in advance.

while (condition) {  
// code 
}

5. Do-While:

Do-while is also used to iterate a set of statements based on a condition. It is mostly used when you need to execute the statements atleast once.

do {  
 // code 
} while (condition);

Functions

Function is a sub-routine which contains set of statements. Usually functions are written when multiple calls are required to same set of statements which increases re-usuability and modularity. Function gets run only when it is called.

How to declare a Function:

return_type function_name(parameters);

How to call a Function:

function_name (parameters)

How to define a Function:

return_type function_name(parameters) {  
 // code
}