Algorithm/Algorithm_full_features/sort/HeapSort.java at master · shellteo/Algorithm · GitHub

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/**

* sorts a sequence of strings from standard input using heapsort.

* The `HeapSort` class provides a static methods for heapsorting an array.

public class HeapSort{

private HeapSort() {}

// rearranges the array in ascending order, using the natural order.

public static void sort(Comparable[] pq) {

int n = pq.length;

for(int k = n / 2; k >= 1; k--) {

sink(pq, k, n);

}

while(n > 1){

exchange(pa, 1, n--);

sink(pq, 1, n);

}

// Helper functions

private static void sink(Comparable[] pq, int k, int n) {

while(2 * k <= n) {

int j = 2 * k;

if(j < n && less(pq, j, j + 1))

j++;

if(!less(pq, k, j))

break;

exchange(pq, k, j);

k = j;

}

// helper functions for comparisons and swaps

// indices are "off-by-one" to support 1-based indexing.

private static boolean less(Comparable[] pq, int i, int j) {

return pq[i - 1].compareTo(pq[j - 1]) < 0;

}

private static void exchange(Object[] pq, int i, int j) {

Object swap = pq[i - 1];

pq[i - 1] = pq[j - 1];

pq[j - 1] = swap;

}

// print

private static void show(Comparable[] a) {

for(int i = 0; i < a.length; i++) {

StdOut.println(a[i]);

}

// test

public static void main(String[] args) {

String[] a = StdIn.readAllStrings();

Heap.sort(a);

show(a);

}

Algorithm/Algorithm_full_features/sort/HeapSort.java at master · shellteo/Algorithm · GitHub

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