Kruti Shah
ca1391130d
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sample gradle build and test / build (pull_request) Successful in 1m4s
72 lines
2.6 KiB
Java
72 lines
2.6 KiB
Java
package com.hithomelabs.princeton1.module5;
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public class Shell<E> extends AbstractCustomSorts<E> {
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// * * sample metadata class to compare no. of sorts and compares, shell sort vs insertion sort
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private class MetaData{
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int compares;
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int swaps;
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}
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/*
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* * We will be performing h sort
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* * Suppose or function to determine subsequent values of h is:
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* * h(i+1) = 3*h(i) + 1; h = 1, 4, 13, 40, 121, ....
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* * h will never be perfectly divisible by 3; further dividing h[i]/3 will give h[i-1]
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* * We want to h-sort using larges value of h smaller than N, followed by smaller values of h
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* * If N = 100, we h-sort by 40, meaning every 40th element will be in order
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* * Then we h-sort by 13, meaning every 40th and every 13th element will be in order and every 40th element will be in order
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* * Finally, when h will come out as 1, it will be same as insertion sort, however by that time the array will almost be sorted
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* * Insertion sort for an almost sorted array is linear time.
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* * As a case study we implement both insertion sort and selection sort for an array of 1000 nos.
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* * And check number of compares and no. of exchanges in each case
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*/
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@Override
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public void sort(E[] arr) {
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MetaData metaData = new MetaData();
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int h = 1;
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while(3*h + 1 < arr.length){
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h = 3*h + 1;
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}
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while(h>=1){
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hsort(arr, h, metaData);
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h= h/3;
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}
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// for(int i=arr.length/10; i>=0; i--){
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// hsort(arr, 3*i+1, metaData);
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// }
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System.out.println("Array sorted (shell sort) with " + metaData.compares + " compares and " + metaData.swaps + " swaps");
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}
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private void hsort(E[] arr, int h, MetaData metadata) {
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for(int i=h; i<arr.length; i=i+1){
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int k = i;
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for(int j=i-h; j>=0; j=j-h){
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metadata.compares++;
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if(less((Comparable<E>) arr[k], arr[j])){
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exch(arr, k, j);
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k = j;
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metadata.swaps++;
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}
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else{
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break;
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}
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}
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}
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}
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/*
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* Sample implementation of insertion sort as h-sort of h = 1
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* Will just be comparing the number of saps taken across both implementations
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*/
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public void insertionSort(E[] arr){
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MetaData metaData = new MetaData();
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int h = 1;
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hsort(arr, h, metaData);
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System.out.println("Array sorted (insertion sort) with " + metaData.compares + " compares and " + metaData.swaps + " swaps");
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}
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}
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