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original.java
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original.java
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package sorting;
import java.io.BufferedReader;
import java.io.InputStreamReader;
import java.util.Random;
import java.util.Arrays;
public class original {
private static int[] arr;
private static int[] arrCopy;
private static BufferedReader read;
private static Random randomGenerator;
private static int size;
private static int random;
private static int n;
private static void printArray() {
System.out.print("[" + arr[0]);
for(int i=1; i<size; i++) {
System.out.print(", " + arr[i]);
}
System.out.println("]");
}
public static void buildheap(){
n=arr.length-1;
for(int i=n/2;i>=0;i--){
heapify(i);
}
}
public static void heapify(int i){
int largest;
int left=2*i;
int right=2*i+1;
if(left <= n && arr[left] > arr[i]){
largest=left;
}
else{
largest=i;
}
if(right <= n && arr[right] > arr[largest]){
largest=right;
}
if(largest!=i){
exchange(i,largest);
heapify(largest);
}
}
public static void exchange(int i, int j){
int t=arr[i];
arr[i]=arr[j];
arr[j]=t;
}
public static void heapsort(){
buildheap();
for(int i=n;i>0;i--){
exchange(0, i);
n=n-1;
heapify(0);
}
}
private static void mergesort(int low, int high) {
// Check if low is smaller then high, if not then the array is sorted
if (low < high) {
// Get the index of the element which is in the middle
int middle = low + (high - low) / 2;
// Sort the left side of the array
mergesort(low, middle);
// Sort the right side of the array
mergesort(middle + 1, high);
// Combine them both
merge(low, middle, high);
}
}
private static void merge(int low, int middle, int high) {
// Copy both parts into the arrCopy array
for (int i = low; i <= high; i++) {
arrCopy[i] = arr[i];
}
int i = low;
int j = middle + 1;
int k = low;
// Copy the smallest values from either the left or the right side back
// to the original array
while (i <= middle && j <= high) {
if (arrCopy[i] <= arrCopy[j]) {
arr[k] = arrCopy[i];
i++;
} else {
arr[k] = arrCopy[j];
j++;
}
k++;
}
// Copy the rest of the left side of the array into the target array
while (i <= middle) {
arr[k] = arrCopy[i];
k++;
i++;
}
}
private static void quicksort(int low, int high) {
int i = low, j = high;
// Get the pivot element from the middle of the list
int pivot = arr[(high+low)/2];
// Divide into two lists
while (i <= j) {
// If the current value from the left list is smaller then the pivot
// element then get the next element from the left list
while (arr[i] < pivot) {
i++;
}
// If the current value from the right list is larger then the pivot
// element then get the next element from the right list
while (arr[j] > pivot) {
j--;
}
// If we have found a values in the left list which is larger then
// the pivot element and if we have found a value in the right list
// which is smaller then the pivot element then we exchange the
// values.
// As we are done we can increase i and j
if (i < j) {
exchange(i, j);
i++;
j--;
} else if (i == j) { i++; j--; }
}
// Recursion
if (low < j)
quicksort(low, j);
if (i < high)
quicksort(i, high);
}
public static void main(String[] args) {
read = new BufferedReader(new InputStreamReader(System.in));
randomGenerator = new Random();
try
{
System.out.print("Please enter array size : ");
size = Integer.parseInt(read.readLine());
System.out.print("Please enter the random range : ");
random = Integer.parseInt(read.readLine());
// create array
arr = new int[size];
arrCopy = new int[size];
// fill array
for(int i=0; i<size; i++) {
arr[i] = arrCopy[i] = randomGenerator.nextInt(random);
}
if (size < 101) {
System.out.println("Initial array:");
printArray();
}
long start = System.currentTimeMillis();
Arrays.sort(arr);
if (size < 101) printArray();
long finish = System.currentTimeMillis();
System.out.println("Arrays.sort: " + (finish-start) + " milliseconds.");
// Heap sort
start = finish;
heapsort();
if (size < 101) printArray();
finish = System.currentTimeMillis();
System.out.println("heapsort: " + (finish-start) + " milliseconds.");
// Quick sort
start = finish;
for(int i=0; i<size; i++) arr[i] = arrCopy[i];
quicksort(0, size-1);
if (size < 101) printArray();
finish = System.currentTimeMillis();
System.out.println("quicksort: " + (finish-start) + " milliseconds.");
// Merge sort, which destroys arrCopy[].
start = finish;
for(int i=0; i<size; i++) arr[i] = arrCopy[i];
mergesort(0, size-1);
if (size < 101) printArray();
finish = System.currentTimeMillis();
System.out.println("mergesort: " + (finish-start) + " milliseconds.");
}
catch(Exception ex){
ex.printStackTrace();
}
}
}