Lecture-9

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Unformatted text preview: Sorting Exercises CPSC 223  ­ ­ Fall 2010 5 9/28/10 Evaluating Sorting Algorithms Number of comparisons –  How many pairs of items are compared within a pass Number of moves –  How many times do we move list items –  Within a list or to a temporary variable •  We often do “swaps” void swap(int& x, int& y) // here just integers { int tmp = x; How many moves in a swap? x = y; 3 y = tmp; } CPSC 223  ­ ­ Fall 2010 Selection Sort The basic idea –  Select (i.e., “find”) the largest item –  Swap it with the last item in the list –  Repeat with items 0 to n – 2 –  Stop when only one item left Pass 1 Ini6al list: 29 10 14 13 (n=4) 13 10 14 29 Pass 2 Pass 3 13 10 14 29 13 10 14 29 13 10 14 29 10 13 14 29 CPSC 223  ­ ­ Fall 2010 6 9/28/10 Selection Sort (based on textbook) void selectionSort(Entry theArray, int n) { for(int i = n - 1; i >= 1; i--) { // passes 1..n-1 int index = 0; for(int j = 1; j < i + 1; j++) { // passes 1..i if(theArray[j] >= theArray[index]) index = j; // not 1 move } // end inner for swap(theArray[index], theArray[i]); // 3 moves } // end outer for } CPSC 223  ­ ­ Fall 2010 Bubble Sort The basic idea:...
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This document was uploaded on 03/18/2014 for the course CPSC 223 at Gonzaga.

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