Internal Sorting

1. Internal Sorting File Sorting Part 2

2. Bubble Sort of an array Inefficient --- O ( N2 ) easy to code, hence unlikely to contain errors Algorithm for outerloop = 1 to N for innerloop = 0 to N-2 if ( item[innerloop] > item[innerloop+1] ) swap item[i] and item[i+1]

3. Selection Sort of an array • Easy to code, less swapping than bubble, but still O ( N2 ) • Splits the array into 2 lists: • one sorted (which slowly grows) • one unsorted (which slowly shrinks) • Algorithm • find the smallest item in unsorted list • swap smallest with start of unsorted list • sorted_size ++; and unsorted_size --;

4. Quick Sort of an array • Very Fast --- O ( N log2 N ) • A pain to program • Algorithm • recursively partition the array into sub-lists • sort infileoutfile …… it's magic !!! animations and comparisons at http://www.sorting-algorithms.com/

5. Sorting a Linked List • Linked Lists are necessary when we don't know the size of the list • Sorting Operations for both arrays and linked lists • comparisons • arrays - need multiple indexes • LL - need multiple pointers • swaps • with big records, LL is easier: • just move a few pointers

6. Insertion Sort of Linked List Oversimplified Algorithm: While not eof newptr = new record with data from file temp = head while (temp != NULL) if (newptr->key < temp->key) insert newptr before temp else temp = temp->next

7. Ordered Binary Tree 40 20 60 10 30 70 Alternative to building Singly Linked List Inserting new node is much easier Traversal to find insertion is log2N So, inserting N items takes N * log2 N compares