iterative and recursive implementation

cpp/Binary Search.py

@@ -1,28 +1,50 @@
 
-"""binary search in c++"""
-
-#include<iostream>
-using namespace std;
-int binarySearch(int arr[], int p, int r, int num) {
- if (p <= r) {
- int mid = (p + r)/2;
- if (arr[mid] == num)
- return mid ;
- if (arr[mid] > num)
- return binarySearch(arr, p, mid-1, num);
- if (arr[mid] > num)
- return binarySearch(arr, mid+1, r, num);
- }
- return -1;
-}
-int main(void) {
- int arr[] = {1, 3, 7, 15, 18, 20, 25, 33, 36, 40};
- int n = sizeof(arr)/ sizeof(arr[0]);
- int num = 33;
- int index = binarySearch (arr, 0, n-1, num);
- if(index == -1)
- cout<< num <<" is not present in the array";
- else
- cout<< num <<" is present at index "<< index <<" in the array";
- return 0;
-}
+
+# iterative implementation of binary search in Python
+
+
+def binary_search(a_list, item):
+ """Performs iterative binary search to find the position of an integer in a given, sorted, list.
+ a_list -- sorted list of integers
+ item -- integer you are searching for the position of
+ """
+
+ first = 0
+ last = len(a_list) - 1
+
+ while first <= last:
+ i = (first + last) / 2
+
+ if a_list[i] == item:
+ return '{item} found at position {i}'.format(item=item, i=i)
+ elif a_list[i] > item:
+ last = i - 1
+ elif a_list[i] < item:
+ first = i + 1
+ else:
+ return '{item} not found in the list'.format(item=item)
+
+
+# recursive implementation of binary search in Python
+
+
+def binary_search_recursive(a_list, item):
+ """Performs recursive binary search of an integer in a given, sorted, list.
+ a_list -- sorted list of integers
+ item -- integer you are searching for the position of
+ """
+
+ first = 0
+ last = len(a_list) - 1
+
+ if len(a_list) == 0:
+ return '{item} was not found in the list'.format(item=item)
+ else:
+ i = (first + last) // 2
+ if item == a_list[i]:
+ return '{item} found'.format(item=item)
+ else:
+ if a_list[i] < item:
+ return binary_search_recursive(a_list[i+1:], item)
+ else:
+ return binary_search_recursive(a_list[:i], item)

cpp/CircularLinkedList.cpp

@@ -1,199 +1,113 @@
 #include <iostream>
-#include <cstdlib>
 
-using namespace std;
+using std::cout;
+using std::cin;
 
-struct node
-{
- int info;
- struct node *next;
+class IntNode{
+ public:
+ /* Constructors */
+ IntNode() {}
+ IntNode(int theData): data(theData), link(NULL) {}
+ IntNode(int theData, IntNode* theLink): data(theData), link(theLink) {}
+ ~IntNode() {} //Destructor
+
+ /* Accessors */
+ int getData() const { return data; }
+ IntNode* getLink() const { return link; }
+
+ /* Mutators */
+ void setData(int theData) { data = theData; }
+ void setLink(IntNode* pointer) { link = pointer; }
+
+ private:
+ int data;
+ IntNode *link;
 };
 
-node *last = nullptr;
+typedef IntNode* IntNodePtr;
 
-void Display()
-{
- struct node *s;
- if (last == nullptr)
- {
- cout << "List is empty, nothing to display" << endl;
- return;
- }
- s = last->next;
- cout << "Circular Link List: " << endl;
- while (s != last)
- {
- cout << s->info << "->";
- s = s->next;
- }
- cout << s->info << endl;
-}
+/* Creates a circular linked list containing "suitors" number of nodes */
+IntNodePtr lineUpSuitors(int suitors);
 
-void createNode(int value)
-{
- struct node *temp;
- temp = new (struct node);
- temp->info = value;
- if (last == nullptr)
- {
- last = temp;
- temp->next = last;
- }
- else
- {
- temp->next = last->next;
- last->next = temp;
- last = temp;
- }
- Display();
-}
+/* Output linked list. Because this demonstration concerns circular lists
+ this function halts output when the pointer of the final element 
+ points back to the first. This function also works for single nodes
+ that refer to themselves. */
+void outputList(IntNodePtr head);
 
-void addBegin(int value)
-{
- if (last == nullptr)
- {
- cout << "First Create the list." << endl;
- return;
- }
- struct node *temp;
- temp = new (struct node);
- temp->info = value;
- temp->next = last->next;
- last->next = temp;
+/* Remove and delete every third node in the circular linked list until
+ one remains. */
+IntNodePtr eliminateSuitors(IntNodePtr);
 
- Display();
+int main(){
+ int numSuitors = 0;
+
+ /* Prompt for suitors */
+ cout << "\nHow many suitors (in integers) does Eve have: ";
+ cin >> numSuitors;
+
+ /* Create circular linked list */
+ IntNodePtr head = lineUpSuitors(numSuitors);
+
+ /* Confirm accuracy of linked list */
+ cout << "\nThe suitors are lined up by number: ";
+ outputList(head);
+
+ /* Eliminate every third suitor until one remains and output result */
+ head = eliminateSuitors(head);
+ cout << "\nEve eliminates every third suitor (starting at 1)"
+ << " and selects suitor: ";
+ outputList(head);
+
+ delete head; //Discard final node
+
+ cout << "\n"; //Extra space for readability
+ return 1;
 }
 
-void addAfter(int value, int pos)
-{
- if (last == nullptr)
- {
- cout << "First Create the list." << endl;
- return;
+/* Creates a circular linked list containing "suitors" number of nodes */
+IntNodePtr lineUpSuitors(int suitors){
+ IntNodePtr head = new IntNode(1), current = head;
+
+ for(int i = 2; i <= suitors; i++){ 
+ current->setLink(new IntNode(i));
+ current = current->getLink();
  }
- struct node *temp, *s;
- s = last->next;
- for (int i = 0; i < pos - 1; i++)
- {
- s = s->next;
- if (s == last->next)
- {
- cout << "There are less than ";
- cout << pos << " in the list" << endl;
- return;
- }
- }
- temp = new (struct node);
- temp->next = s->next;
- temp->info = value;
- s->next = temp;
-
- if (s == last)
- {
- last = temp;
- }
- Display();
+
+ current->setLink(head);
+
+ return head;
 }
 
-void Delete(int value)
-{
- struct node *temp, *s;
- s = last->next;
-
- if (last->next == last && last->info == value)
- {
- temp = last;
- last = nullptr;
- free(temp);
- Display();
- return;
- }
- if (s->info == value)
- {
- temp = s;
- last->next = s->next;
- free(temp);
- Display();
- return;
- }
- while (s->next != last)
- {
-
- if (s->next->info == value)
- {
- temp = s->next;
- s->next = temp->next;
- free(temp);
- cout << "Element " << value;
- cout << " deleted from the list" << endl;
- Display();
- return;
- }
- s = s->next;
- }
-
- if (s->next->info == value)
- {
- temp = s->next;
- s->next = last->next;
- free(temp);
- last = s;
- Display();
- return;
+/* Output linked list. Because this demonstration concerns circular lists
+ this function halts output when the pointer of the final element 
+ points back to the first. This function also works for single nodes
+ that refer to themselves. */
+void outputList(IntNodePtr head){
+ IntNodePtr current = head;
+
+ cout << current->getData();
+
+ while(current->getLink() != head){
+ current = current->getLink();
+ cout << current->getData();
  }
- cout << "Element " << value << " not found in the list" << endl;
+
+ cout << "\n"; //Extra space for readability
 }
 
-int main()
-{
- int choice, element, position;
-
- while (1)
- {
- cout << "1.Create Node" << endl;
- cout << "2.Add at beginning" << endl;
- cout << "3.Add after a position" << endl;
- cout << "4.Delete" << endl;
- cout << "5.Quit" << endl;
- cout << "Enter your choice : ";
- cin >> choice;
- switch (choice)
- {
- case 1:
- cout << "Enter the element: ";
- cin >> element;
- createNode(element);
- cout << endl;
- break;
- case 2:
- cout << "Enter the element: ";
- cin >> element;
- addBegin(element);
- cout << endl;
- break;
- case 3:
- cout << "Enter the element: ";
- cin >> element;
- cout << "Insert element after position: ";
- cin >> position;
- addAfter(element, position);
- cout << endl;
- break;
- case 4:
- if (last == nullptr)
- {
- cout << "List is empty, nothing to delete" << endl;
- break;
- }
- cout << "Enter the element for deletion: ";
- cin >> element;
- Delete(element);
- cout << endl;
- break;
- case 5:
- exit(0);
- default:
- cout << "Wrong choice" << endl;
- }
+/* Remove and delete every third node in the circular linked list until
+ one remains. */
+IntNodePtr eliminateSuitors(IntNodePtr head){
+ IntNodePtr current = head->getLink(), next = current->getLink();
+
+ while(current->getLink() != current){
+ current->setLink(next->getLink());
+ delete next;
+ head = current->getLink();
+ current = head->getLink();
+ next = current->getLink();
  }
+
+ return current;
 }