75 lines
2.2 KiB
Java
75 lines
2.2 KiB
Java
package Sorts;
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/* Java program for Bitonic Sort. Note that this program
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works only when size of input is a power of 2. */
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public class BitonicSort {
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/* The parameter dir indicates the sorting direction,
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ASCENDING or DESCENDING; if (a[i] > a[j]) agrees
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with the direction, then a[i] and a[j] are
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interchanged. */
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void compAndSwap(int a[], int i, int j, int dir) {
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if ((a[i] > a[j] && dir == 1) || (a[i] < a[j] && dir == 0)) {
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// Swapping elements
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int temp = a[i];
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a[i] = a[j];
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a[j] = temp;
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}
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}
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/* It recursively sorts a bitonic sequence in ascending
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order, if dir = 1, and in descending order otherwise
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(means dir=0). The sequence to be sorted starts at
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index position low, the parameter cnt is the number
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of elements to be sorted.*/
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void bitonicMerge(int a[], int low, int cnt, int dir) {
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if (cnt > 1) {
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int k = cnt / 2;
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for (int i = low; i < low + k; i++) compAndSwap(a, i, i + k, dir);
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bitonicMerge(a, low, k, dir);
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bitonicMerge(a, low + k, k, dir);
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}
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}
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/* This funcion first produces a bitonic sequence by
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recursively sorting its two halves in opposite sorting
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orders, and then calls bitonicMerge to make them in
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the same order */
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void bitonicSort(int a[], int low, int cnt, int dir) {
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if (cnt > 1) {
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int k = cnt / 2;
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// sort in ascending order since dir here is 1
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bitonicSort(a, low, k, 1);
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// sort in descending order since dir here is 0
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bitonicSort(a, low + k, k, 0);
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// Will merge whole sequence in ascending order
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// since dir=1.
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bitonicMerge(a, low, cnt, dir);
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}
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}
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/*Caller of bitonicSort for sorting the entire array
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of length N in ASCENDING order */
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void sort(int a[], int N, int up) {
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bitonicSort(a, 0, N, up);
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}
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/* A utility function to print array of size n */
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static void printArray(int arr[]) {
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int n = arr.length;
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for (int i = 0; i < n; ++i) System.out.print(arr[i] + " ");
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System.out.println();
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}
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public static void main(String args[]) {
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int a[] = {3, 7, 4, 8, 6, 2, 1, 5};
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int up = 1;
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BitonicSort ob = new BitonicSort();
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ob.sort(a, a.length, up);
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System.out.println("\nSorted array");
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printArray(a);
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}
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}
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