Merge pull request #327 from TesseractCoding/master

mpr

C/README.md

@@ -135,6 +135,7 @@
 - [Postfix to Infix Conversion](ds/postfixToInfix.c)
 - [Prefix to Postfix Conversion](ds/prefix-to-postfix.c)
 - [Morris Order Traversal ] (ds/Morris.c)
+- [Hash Table Implementation](ds/hashtable.c)
 
 
 ## Searching

C/ds/hashtable.c

@@ -0,0 +1,338 @@
+/*
+HASH TABLE USING LINEAR PROBING
+ A hash function is a function that maps all the keys to the slots of an array. it is given a key and  an array, the hash function can make a suggestion as to where the index of the key should be stored in the   array.
+ 
+ Linear probing -
+ -starting with index j where collison occurred
+ -it looks for next available index by using hash function
+ -And all the attributes for the index will be inserted
+ 
+Hash Table implemented in c which includes all CRUD operations (insert, display, update , delete)      which menu driven and also included to return the size of table instantly.
+(here updating happens if the key already present in table )
+*/
+
+#include <stdio.h>
+#include <stdlib.h>
+
+//structure of the each element in the table 
+struct set
+{
+  int key;
+  int data;
+  int collision;
+};
+
+//declare hash table and maximaum capacity
+struct set *array;
+int capacity = 10;
+int size = 0;
+
+//Hashing function to get the index for a given key
+int hashFunction(int key)
+{
+  return (key % capacity);
+}
+
+//to check whether prime or not
+int checkPrime(int n)
+{
+  int i;
+  if (n == 1 || n == 0)
+  {
+  return 0;
+  }
+  for (i = 2; i < n / 2; i++)
+  {
+  if (n % i == 0)
+  {
+    return 0;
+  }
+  }
+  return 1;
+}
+
+//here , next prime no of capacity is obtained ,this will be used in hashfunction to get the index
+int getPrime(int n)
+{
+  if (n % 2 == 0)
+  {
+  n++;
+  }
+  while (!checkPrime(n))
+  {
+  n += 2;
+  }
+  return n;
+}
+
+//initialising the array(table) along with its attributes to 0
+void init_array()
+{
+  capacity = getPrime(capacity);
+  array = (struct set *)malloc(capacity * sizeof(struct set));
+  for (int i = 0; i < capacity; i++)
+  {
+  array[i].key = 0;
+  array[i].data = 0;
+  array[i].collision = 0;
+  }
+}
+
+//to insert to hash table
+void insert(int key, int data)
+{
+  /*
+  if index is already occupied then using linear probing to get the available index ,show if 
+  collision occured and print index value where the key is being inserted
+  */
+  int index = hashFunction(key);
+  if (array[index].data == 0)
+  {
+  array[index].key = key;
+  array[index].data = data;
+  size++;
+  printf("\n Key (%d) has been inserted \n\n", key);
+  }
+  else if (array[index].key == key)
+  {
+  array[index].data = data;
+  }
+  else
+  {
+	  array[index].collision = array[index].collision+1;
+  while(array[index].key != 0){
+	  index=(index+1)%capacity;
+	  if(array[index].key == key){
+		  break;
+	  }
+  }
+   if (array[index].data == 0)
+  {
+  array[index].key = key;
+  array[index].data = data;
+  size++;
+   printf("\n Collision occured  \n\n");
+   printf("\n Key (%d) has been inserted at %d using linear probing \n\n", key,index);
+  }
+  else if (array[index].key == key)
+  {
+  array[index].data = data;
+  }
+  }
+}
+
+//remove element from the table by using key
+void remove_element(int key)
+{
+	/*
+	if key exist, then using hashFunction ,we get the index .If not present at index then searching the table to find the key
+	*/
+  int index = hashFunction(key);
+  if(array[index].collision>0){
+	  while(array[index].key!=key){
+		  index++;
+	  }
+  if (array[index].data == 0)
+  {
+  printf("\n This key does not exist \n");
+  }
+  else
+  {
+  array[index].key = 0;
+  array[index].data = 0;
+  array[index].collision--;
+  size--;
+  printf("\n Key (%d) has been removed \n", key);
+  } 
+  }
+  else{
+  if (array[index].data == 0)
+  {
+  printf("\n This key does not exist \n");
+  }
+  else
+  {
+  array[index].key = 0;
+  array[index].data = 0;
+  size--;
+  printf("\n Key (%d) has been removed \n", key);
+  }
+  }
+}
+
+//display the hashtable
+void display()
+{
+  int i;
+  for (i = 0; i < capacity; i++)
+  {
+  if (array[i].data == 0)
+  {
+    printf("\n array[%d]: / ", i);
+  }
+  else
+  {
+    printf("\n key: %d array[%d]: %d \t", array[i].key, i, array[i].data);
+  }
+  }
+}
+
+//to get the size of hashtable
+int size_of_hashtable()
+{
+  return size;
+}
+
+//driver code
+int main()
+{
+  int choice, key, data, n;
+  int c = 0;
+  init_array();
+	printf("\n\t\t************HashTable implementation using linear probing************\n\n");
+
+	/*
+	Menu driven code which includes inserting,deleting,getting size of table, display the table.
+	*/
+  do
+  {
+  printf("\n1.Insert item in the Hash Table"
+     "\n2.Remove item from the Hash Table"
+     "\n3.Check the size of Hash Table"
+     "\n4.Display a Hash Table"
+	 "\n5.exit"
+     "\n\n Please enter your choice: ");
+  scanf("%d", &choice);
+  switch (choice)
+  {
+  case 1:
+    printf("Enter key -:\t");
+    scanf("%d", &key);
+    printf("Enter data -:\t");
+    scanf("%d", &data);
+    insert(key, data);
+    break;
+  case 2:
+    printf("Enter the key to delete-:");
+    scanf("%d", &key);
+    remove_element(key);
+    break;
+  case 3:
+    n = size_of_hashtable();
+    printf("Size of Hash Table is-:%d\n", n);
+    break;
+  case 4:
+    display();
+	printf("\n\n");
+    break;
+  default:
+    exit(0);
+  }
+  } while (1);
+}
+/*
+
+Sample I/O and O/P
+************HashTable implementation using linear probing************
+
+
+1.Insert item in the Hash Table
+2.Remove item from the Hash Table
+3.Check the size of Hash Table
+4.Display a Hash Table
+5.exit
+
+ Please enter your choice:1
+ Enter key -:    33
+Enter data -:   123
+
+ Key (33) has been inserted
+
+
+1.Insert item in the Hash Table
+2.Remove item from the Hash Table
+3.Check the size of Hash Table
+4.Display a Hash Table
+5.exit
+
+ Please enter your choice:1
+Enter key -:    34
+Enter data -:   322
+
+ Key (34) has been inserted
+
+
+1.Insert item in the Hash Table
+2.Remove item from the Hash Table
+3.Check the size of Hash Table
+4.Display a Hash Table
+5.exit
+
+ Please enter your choice:1
+Enter key -:    33
+Enter data -:   989
+
+1.Insert item in the Hash Table
+2.Remove item from the Hash Table
+3.Check the size of Hash Table
+4.Display a Hash Table
+5.exit
+
+ Please enter your choice:1
+Enter key -:    45
+Enter data -:   231
+
+ Collision occured
+
+ Key (45) has been inserted at 2 using linear probing
+
+1.Insert item in the Hash Table
+2.Remove item from the Hash Table
+3.Check the size of Hash Table
+4.Display a Hash Table
+5.exit
+
+ Please enter your choice:4
+ key: 33 array[0]: 989
+ key: 34 array[1]: 322
+ key: 45 array[2]: 231
+ array[3]: /
+ array[4]: /
+ array[5]: /
+ array[6]: /
+ array[7]: /
+ array[8]: /
+ array[9]: /
+ array[10]: /
+
+1.Insert item in the Hash Table
+2.Remove item from the Hash Table
+3.Check the size of Hash Table
+4.Display a Hash Table
+5.exit
+
+ Please enter your choice:2
+ Enter the key to delete-:45
+
+ Key (45) has been removed
+
+1.Insert item in the Hash Table
+2.Remove item from the Hash Table
+3.Check the size of Hash Table
+4.Display a Hash Table
+5.exit
+
+ Please enter your choice:3
+ Size of Hash Table is-:2
+
+1.Insert item in the Hash Table
+2.Remove item from the Hash Table
+3.Check the size of Hash Table
+4.Display a Hash Table
+5.exit
+
+ Please enter your choice:5
+ 
+
+Time and space Complexities of a Hash Table/Map is O(n)
+*/