CSS 133 Computer Programming for Engineers II Linked Lists, Stack, Queue Professor Pisan 1 Doubly Linked List What can we do that we could not before? What is the disadvantage? How would removeNode change? Review Code: https://github.com/pisan133/doubly-linkedlist Lab: printBackward, findLargest, findSmallest, swapNodes 2 Extending Linked Lists Linked List: flexible ● insertAtFront, insertAtBack ● addBefore, addAfter ● contains ● empty ● removeNode, swap ● size Stack: LIFO - Last In, First Out ● push, pop, top Queue: FIFO - First in, First Out ● push, pop, front ● older versions: enqueue, dequeue, front 3 Linked List vs Array Arrays ● Fixed size ● Insert anywhere other than the end takes extra time ● Random access to elements possible ○ Binary search for sorted array ● Forward/backward traversal Linked List ● Extendable ● Has to allocate/deallocate memory ● Flexible ○ Need front and back ptr if we want to insert at end ○ Need double linked list to traverse forwards and backwards ● No random access ○ Maintaining a sorted list easy ○ Sorting is time consuming ○ No binary search 4 Stack LIFO - Last In, First Out ● push, pop, top ● Function call, push return address onto the stack ● Backtracking - remember the series of choices, when stuck, go back and change the choice ○ http://cs.lmu.edu/~ray/notes/backtracking/ ● Reverse-Polish Notation: 3 4 + ○ Efficient for computer math. No parentheses. ○ Operators applied to the operands at the bottom of the stack 5 Implementation Array ● Have a maximum stack size ● Keep track of index of the last element ● First element goes to index 0, next one at index 1, etc Linked List ● Use insertAtFront for push, removeFromFront for pop (alternatively insert and remove at back) 6 Queue FIFO - First in, First Out ● push, pop, front ● older versions: enqueue, dequeue, front Store objects and process them in the order they came ● Printer queue -- print the jobs in order 7 Implementation Array ● Keep track of front and back of queue ○ First element goes to index 0, next one at index 1, etc ○ Dequeue removes element at index-0, then index-1, etc ● Option 1 (expensive) ○ Fill the array, shift all elements when we reach end of array ● Option 2: ○ Treat the array as circular ○ When we get to end of the array, wrap around and use the beginning Linked List ● Use insertAtBack for enqueue, removeFromFront for dequeue 8 reverse a Linked List 0 0 20 30 40 50 20 30 40 50 void reverse(Node* head) { // only have dummy head if (head->nextPtr == NULL || head->nextPtr->nextPtr == NULL) return; Node* a = NULL; Node* b = head->nextPtr; // currently have a-->b, want to get b-->a and advance while (b != NULL) { Node* c = b->nextPtr; b->nextPtr = a; a = b; b = c; } // point head to the front (which used to be last) head->nextPtr = a; } 9 Lab-3: C Doubly Linked List https://github.com/pisan133/doubly-linkedlist printBackward, findLargest, findSmallest, swapNodes // Linked list example from class exercise https://github.com/pisan133/linked-list 10 Review ● C Functions ○ printf, fgets, atoi, atof, typedef, struct, sizeof ○ malloc, free ○ casting ● Unix commands ○ ls, cd, pwd, mkdir, rmdir, chmod, cat, man, cp, mv, man, nano ● Bitwise Operators: & | ^ << >> ~ ● Singly Linked List structure ○ addBefore, addAfter, addSorted, removeNode, swap ● Doubly Linked List structure ● String functions ○ strlen, strcpy, strcat, strcmp ● Stack and Queue ● In-class exercises: BMI, Secret Key, Imaginary Numbers Exam will only have C programming not C++ 11 Clear as Mud Anonymous end of class feedback 1. Encourage student reflection 2. Assist students in using time to study effectively 3. Provides information to instructor to correct misconceptions 4. Is more effective than asking for questions 5. Is fun! http://bit.ly/ypmuddy 12.