babby's first linked list

cs161BW8/agenda.org

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+* Agenda
+** Tuesday
+ + Pointers as arguments to functions
+   + Pointers by value
+   + Pointers by reference
+ + Structs and pointers to makes lists
+   + Finally
+ + Long example: linked lists with pointers
+   + First: combining structs and pointers
+     + Pointers to structs
+     + Structs with pointers
+   + Second: A recursively defined struct
+     + Saved from circularity with the power of pointers!
+   + Third: Traversing our linked list
+     + Recursive function definitions
+     + Adding to the front of the list
+     + Adding to the back of the list
+     + Removing from the front of the list
+     + Removing from the end of the list
+     + Adding/removing from arbitrary positions
+   + Fourth: bonus operations
+     + Summing all elements of a list
+** Thursday
+ + Linux, linux, and more linux
+ + Spillover from Tuesday

cs161BW8/listStruct.cpp

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+#include <iostream>
+using namespace std;
+
+/*
+  Goal:
+  Implement lists not with arrays but with
+  structs that contain pointers
+
+  commonly called linked lists
+
+
+  |1| -> |2| -> |5| -> |6| -> nullptr
+*/
+
+
+// bad definition leads to size
+// equation of the form
+// size(struct) = size(struct) + 1
+
+// good definition leads to size equation
+// of the form
+// size(struct) = 1 + 1
+struct Node {
+  int data;
+  Node* next;
+};
+
+Node* makeNode(int v){
+  Node* n = new Node;
+  n->data = v;
+  n->next = nullptr;
+  return n;
+}
+
+// revist this when we add deletion
+void append(Node* lst, int v){
+  if(lst->next == nullptr){
+    Node* n = makeNode(v);
+    lst->next = n;
+  }
+  else{
+    append(lst->next,v);
+  }
+}
+
+void printList(Node* lst){
+  if(lst != nullptr){
+    cout << lst->data << " ";
+    printList(lst->next);
+  }
+  else{
+    cout << endl;
+  }
+}
+
+int main(){
+  Node* ourList = makeNode(0);
+  append(ourList,1);
+  append(ourList,2);
+  append(ourList,3);
+
+  printList(ourList);
+
+  return 0;
+}

cs161BW8/listStruct1.cpp

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+#include <iostream>
+using namespace std;
+
+/*
+  Goal:
+  Implement lists not with arrays but with
+  structs that contain pointers
+
+  commonly called linked lists
+
+
+  |1| -> |2| -> |5| -> |6| -> nullptr
+*/
+
+
+// bad definition leads to size
+// equation of the form
+// size(struct) = size(struct) + 1
+
+// good definition leads to size equation
+// of the form
+// size(struct) = 1 + 1
+struct Node {
+  int data;
+  Node* next;
+};
+
+Node* makeNode(int v){
+  Node* n = new Node;
+  n->data = v;
+  n->next = nullptr;
+  return n;
+}
+
+// revist this when we add deletion
+void append(Node* lst, int v){
+  if(lst->next == nullptr){
+    Node* n = makeNode(v);
+    lst->next = n;
+  }
+  else{
+    append(lst->next,v);
+  }
+}
+
+void printList(Node* lst){
+  if(lst != nullptr){
+    cout << lst->data << " ";
+    printList(lst->next);
+  }
+  else{
+    cout << endl;
+  }
+}
+
+int main(){
+  Node* ourList = makeNode(0);
+  append(ourList,1);
+  append(ourList,2);
+  append(ourList,3);
+
+  printList(ourList);
+
+  return 0;
+}

cs161BW8/listStructStr.cpp

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+#include <iostream>
+using namespace std;
+
+/*
+  Goal:
+  Implement lists not with arrays but with
+  structs that contain pointers
+
+  commonly called linked lists
+
+
+  |1| -> |2| -> |5| -> |6| -> nullptr
+*/
+
+
+// bad definition leads to size
+// equation of the form
+// size(struct) = size(struct) + 1
+
+// good definition leads to size equation
+// of the form
+// size(struct) = 1 + 1
+struct Node {
+  int data;
+  Node* next;
+};
+
+Node* makeNode(int v){
+  Node* n = new Node;
+  n->data = v;
+  n->next = nullptr;
+  return n;
+}
+
+// revist this when we add deletion
+void append(Node* lst, int v){
+  if(lst->next == nullptr){
+    Node* n = makeNode(v);
+    lst->next = n;
+  }
+  else{
+    append(lst->next,v);
+  }
+}
+
+void printList(Node* lst){
+  if(lst != nullptr){
+    cout << lst->data << " ";
+    printList(lst->next);
+  }
+  else{
+    cout << endl;
+  }
+}
+
+int main(){
+  Node* ourList = makeNode(0);
+  append(ourList,1);
+  append(ourList,2);
+  append(ourList,3);
+
+  printList(ourList);
+
+  return 0;
+}

cs161BW8/listStructT.cpp

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+#include <iostream>
+using namespace std;
+
+/*
+  Goal:
+  Implement lists not with arrays but with
+  structs that contain pointers
+
+  commonly called linked lists
+
+
+  |1| -> |2| -> |5| -> |6| -> nullptr
+*/
+
+
+// bad definition leads to size
+// equation of the form
+// size(struct) = size(struct) + 1
+
+// good definition leads to size equation
+// of the form
+// size(struct) = 1 + 1
+template <typename T>
+struct Node {
+  T data;
+  Node<T>* next;
+};
+
+template <typename T>
+Node<T>* makeNode(T d){
+  Node<T>* n = new Node<T>;
+  n->data = d;
+  n->next = nullptr;
+  return n;
+}
+
+// revist this when we add deletion
+template <typename T>
+void append(Node<T>* lst, T d){
+  if(lst->next == nullptr){
+    Node<T>* n = makeNode(d);
+    lst->next = n;
+  }
+  else{
+    append(lst->next,d);
+  }
+}
+
+template <typename T>
+void printList(Node<T>* lst){
+  if(lst != nullptr){
+    cout << lst->data << " ";
+    printList(lst->next);
+  }
+  else{
+    cout << endl;
+  }
+}
+
+int main(){
+  Node<int>* ourList = makeNode(0);
+  append(ourList,1);
+  append(ourList,2);
+  append(ourList,3);
+
+  printList(ourList);
+
+  return 0;
+}

cs161BW8/pointerFunc.cpp

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+#include <iostream>
+using namespace std;
+
+/*
+  function that takes two pointers as arguments,
+  averages the values stored at the pointers,
+  then swaps the values, returns the average
+*/
+int averageAndSwap(int* p1, int* p2){
+  int v1 = *p1; //follow the address in p1 to the value v1
+  int v2 = *p2; //same for p2 and v2
+
+  *p1 = v2;
+  *p2 = v1;
+
+  return (v1 + v2) / 2;
+}
+
+int averageAndSwapRef(int &x1, int &x2){
+  int temp = x1;
+
+  x1 = x2;
+  x2 = temp;
+
+  return (x1 + x2)/2;
+}
+
+int main(){
+  int var1 = 10;
+  int var2 = 20;
+
+  averageAndSwap(&var1, &var2);
+
+  cout << var1 << " " << var2 << endl;
+
+  averageAndSwapRef(var1,var2);
+
+  cout << var1 << " " << var2 << endl;
+
+  return 0;
+}

cs161BW8/pointerFuncOnceMore.cpp

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+#include <iostream>
+using namespace std;
+
+int averageAndSwapPtrRef(int* &p1, int* &p2){
+  int* temp = p1;
+  p1 = p2;
+  p2 = temp;
+
+  return (*p1 + *p2)/2;
+}
+
+int averageWrong(int* p1, int* p2){
+  int* temp = p1;
+  p1 = p2;
+  p2 = temp;
+
+  return (*p1 + *p2)/2;
+}
+
+
+int main(){
+  int* p1 = new int;
+  int* p2 = new int;
+
+  *p1 = 10;
+  *p2 = 20;
+
+  cout << "Address in p1: "<< p1 << endl;
+  cout << "Address in p2: "<< p2 << endl;
+
+  averageWrong(p1,p2);
+
+  cout << "Address in p1: "<< p1 << endl;
+  cout << "Address in p2: "<< p2 << endl;
+
+  cout << "Value in p1: " << *p1 << endl;
+  cout << "Value in p2: " << *p2 << endl;
+
+  delete p1;
+  delete p2;
+
+  return 0;
+}