Lecture13

# Lecture13 - Applications of Heaps EECS 233-2 Application#1...

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Unformatted text preview: Applications of Heaps EECS 233-2- Application #1: Heap-sort Sorting algorithms: given an arbitrary array, re-position the items in the array in ascending or descending order A naïve algorithm (we will learn more later) It isn ’ t efFcient ( O (n 2 )), because it performs a linear scan to Fnd the smallest remaining item ( O (n) steps per scan). 4 6 11 9 15 5 7 16 13 15 6 11 9 4 5 7 16 13 15 6 11 9 4 7 5 16 13 15 13 11 9 4 7 5 16 6-3- Heap-Sort Heap-sort is a sorting algorithm that repeatedly fnds the largest remaining item From a heap and puts it in place. void heapSort(T arr, int length, int numItems) { // Turn the array into a max-at-top heap. Heap<T> heap = new Heap<T>(arr, length, numItems); int endUnsorted = numItems - 1; while (endUnsorted > 0) { // Get the largest remaining item and put it to the end T largestRemaining = heap.remove(); arr[endUnsorted] = largestRemaining; endUnsorted--; } } It is eFfcient ( O (N log N)): O(N) to turn the array into a heap O(log N) to remove the largest remaining item N above removals-4-...
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Lecture13 - Applications of Heaps EECS 233-2 Application#1...

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