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* BAEL-4409 : codes have been added

* BAEL-4409 : how to implement min-max heap in java

* BAEL-4409 : how to implement min-max heap in java
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Arash Ariani 2021-06-20 18:21:00 +04:30 committed by GitHub
parent 51ceab1ac3
commit dd715d4e70
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344
data-structures/src/main/java/com/baeldung/minmaxheap/MinMaxHeap.java Normal file
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package com.baeldung.minmaxheap;
import java.util.*;
/**
* Created by arash on 15.06.21.
*/
public class MinMaxHeap<T extends Comparable<T>> {
private List<T> array;
private int capacity;
private int indicator;
MinMaxHeap(int capacity) {
array = new ArrayList<>();
this.capacity = capacity;
indicator = 1;
}
MinMaxHeap(List<T> array) {
this.array = array;
this.capacity = array.size();
this.indicator = array.size() + 1;
}
public List<T> getMinMaxHeap() {
return array;
}
public List<T> create() {
for (int i = Math.floorDiv(array.size(), 2); i >= 1; i--) {
pushDown(array, i);
}
return array;
}
private void pushDown(List<T> array, int i) {
if (isEvenLevel(i)) {
pushDownMin(array, i);
} else {
pushDownMax(array, i);
}
}
private void pushDownMin(List<T> h, int i) {
while (getLeftChildIndex(i) < indicator) {
int indexOfSmallest = getIndexOfSmallestChildOrGrandChild(h, i);
if (h.get(indexOfSmallest - 1).compareTo(h.get(i - 1)) < 0) {
if (getParentIndex(getParentIndex(indexOfSmallest)) == i) {
if (h.get(indexOfSmallest - 1).compareTo(h.get(i - 1)) < 0) {
swap(indexOfSmallest - 1, i - 1, h);
if (h.get(indexOfSmallest - 1).compareTo(h.get(getParentIndex(indexOfSmallest) - 1)) > 0) {
swap(indexOfSmallest - 1, getParentIndex(indexOfSmallest) - 1, h);
}
}
} else if (h.get(indexOfSmallest - 1).compareTo(h.get(i - 1)) < 0) {
swap(indexOfSmallest - 1, i - 1, h);
}
} else {
break;
}
i = indexOfSmallest;
}
}
private void pushDownMax(List<T> h, int i) {
while (getLeftChildIndex(i) < indicator) {
int indexOfGreatest = getIndexOfGreatestChildOrGrandChild(h, i);
if (h.get(indexOfGreatest - 1).compareTo(h.get(i - 1)) > 0) {
if (getParentIndex(getParentIndex(indexOfGreatest)) == i) {
if (h.get(indexOfGreatest - 1).compareTo(h.get(i - 1)) > 0) {
swap(indexOfGreatest - 1, i - 1, h);
if (h.get(indexOfGreatest - 1).compareTo(h.get(getParentIndex(indexOfGreatest) - 1)) < 0) {
swap(indexOfGreatest - 1, getParentIndex(indexOfGreatest) - 1, h);
}
}
} else if (h.get(indexOfGreatest - 1).compareTo(h.get(i - 1)) > 0) {
swap(indexOfGreatest - 1, i - 1, h);
}
} else {
break;
}
i = indexOfGreatest;
}
}
private void swap(int i, int j, List<T> h) { //switch data at x with data at y
T temp = h.get(i);
h.set(i, h.get(j));
h.set(j, temp);
}
private int getLeftChildIndex(int i) {
return 2 * i;
}
private int getRightChildIndex(int i) {
return ((2 * i) + 1);
}
private int getParentIndex(int i) {
return i / 2;
}
private int getGrandparentIndex(int i) {
return i / 4;
}
private boolean isEvenLevel(int i) {
return logBase2(i) % 2 == 0;
}
private int logBase2(int num) {
return (int) (Math.log(num) / Math.log(2));
}
private int getMinChildIndex(int i) {
return array.get(getLeftChildIndex(i)).compareTo(array.get(getRightChildIndex(i))) < 0 ? getLeftChildIndex(i) : getRightChildIndex(i);
}
private int getMaxChildIndex(int i) {
return array.get(getLeftChildIndex(i)).compareTo(array.get(getRightChildIndex(i))) > 0 ? getLeftChildIndex(i) : getRightChildIndex(i);
}
private int getIndexOfSmallestChildOrGrandChild(List<T> h, int i) {
int minIndex = getLeftChildIndex(i);
T minValue = h.get(minIndex - 1);
if (getRightChildIndex(i) < indicator) {
if (h.get(getRightChildIndex(i) - 1).compareTo(minValue) < 0) {
minValue = h.get(getRightChildIndex(i));
minIndex = getRightChildIndex(i);
}
} else {
return minIndex;
}
if (getLeftChildIndex(getLeftChildIndex(i)) < indicator) {
if (h.get(getLeftChildIndex(getLeftChildIndex(i)) - 1).compareTo(minValue) < 0) {
minValue = h.get(getLeftChildIndex(getLeftChildIndex(i)) - 1);
minIndex = getLeftChildIndex(getLeftChildIndex(i));
}
} else {
return minIndex; //if no leftmost grandchild
}
if (getRightChildIndex(getLeftChildIndex(i)) < indicator) {
if (h.get(getRightChildIndex(getLeftChildIndex(i)) - 1).compareTo(minValue) < 0) {
minValue = h.get(getRightChildIndex(getLeftChildIndex(i)) - 1);
minIndex = getRightChildIndex(getLeftChildIndex(i));
}
} else {
return minIndex; //if no left-right grandchild
}
if (getLeftChildIndex(getRightChildIndex(i)) < indicator) {
if (h.get(getLeftChildIndex(getRightChildIndex(i)) - 1).compareTo(minValue) < 0) {
minValue = h.get(getLeftChildIndex(getRightChildIndex(i)) - 1);
minIndex = getLeftChildIndex(getRightChildIndex(i));
}
} else {
return minIndex; //if no right-left grandchild
}
if (getRightChildIndex(getRightChildIndex(i)) < indicator) {
if (h.get(getRightChildIndex(getRightChildIndex(i)) - 1).compareTo(minValue) < 0) {
minValue = h.get(getRightChildIndex(getRightChildIndex(i)) - 1);
minIndex = getRightChildIndex(getRightChildIndex(i));
}
} else {
return minIndex;
}
return minIndex;
}
private int getIndexOfGreatestChildOrGrandChild(List<T> h, int i) {
int maxIndex = getLeftChildIndex(i); //we know left child exists
T maxValue = h.get(maxIndex - 1);
if (getRightChildIndex(i) < indicator) {
if (h.get(getRightChildIndex(i) - 1).compareTo(maxValue) > 0) {
maxValue = h.get(getRightChildIndex(i) - 1);
maxIndex = getRightChildIndex(i);
}
} else {
return maxIndex;
}
if (getLeftChildIndex(getLeftChildIndex(i)) < indicator) {
if (h.get(getLeftChildIndex(getLeftChildIndex(i)) - 1).compareTo(maxValue) > 0) {
maxValue = h.get(getLeftChildIndex(getLeftChildIndex(i)) - 1);
maxIndex = getLeftChildIndex(getLeftChildIndex(i));
}
} else {
return maxIndex; //if no leftmost grandchild
}
if (getRightChildIndex(getLeftChildIndex(i)) < indicator) {
if (h.get(getRightChildIndex(getLeftChildIndex(i)) - 1).compareTo(maxValue) > 0) {
maxValue = h.get(getRightChildIndex(getLeftChildIndex(i)) - 1);
maxIndex = getRightChildIndex(getLeftChildIndex(i));
}
} else {
return maxIndex; //if no left-right grandchild
}
if (getLeftChildIndex(getRightChildIndex(i)) < indicator) {
if (h.get(getLeftChildIndex(getRightChildIndex(i)) - 1).compareTo(maxValue) > 0) {
maxValue = h.get(getLeftChildIndex(getRightChildIndex(i)) - 1);
maxIndex = getLeftChildIndex(getRightChildIndex(i));
}
} else {
return maxIndex;
}
if (getRightChildIndex(getRightChildIndex(i)) < indicator) {
if (h.get(getRightChildIndex(getRightChildIndex(i)) - 1).compareTo(maxValue) > 0) {
maxValue = h.get(getRightChildIndex(getRightChildIndex(i)) - 1);
maxIndex = getRightChildIndex(getRightChildIndex(i));
}
} else {
return maxIndex;
}
return maxIndex;
}
public boolean isFull() {
return indicator == this.capacity + 1;
}
public boolean isEmpty() {
return indicator == 1;
}
public void insert(T item) {
if (isEmpty()) {
array.add(item);
indicator++;
} else if (!isFull()) {
array.add(item);
pushUp(array, indicator);
indicator++;
} else {
throw new RuntimeException("invalid operation !!!");
}
}
private void pushUpMin(List<T> h, int i) {
while (hasGrandparent(i) && h.get(i - 1).compareTo(h.get(getGrandparentIndex(i) - 1)) < 0) {
swap(i - 1, getGrandparentIndex(i) - 1, h);
i = getGrandparentIndex(i);
}
}
private void pushUpMax(List<T> h, int i) {
while (hasGrandparent(i) && h.get(i - 1).compareTo(h.get(getGrandparentIndex(i) - 1)) > 0) {
swap(i - 1, getGrandparentIndex(i) - 1, h);
i = getGrandparentIndex(i);
}
}
private boolean hasGrandparent(int i) {
return getParentIndex(i) > 1;
}
private void pushUp(List<T> h, int i) {
if (i != 1) {
if (isEvenLevel(i)) {
if (h.get(i - 1).compareTo(h.get(getParentIndex(i) - 1)) < 0) {
pushUpMin(h, i);
} else {
swap(i - 1, getParentIndex(i) - 1, h);
i = getParentIndex(i);
pushUpMax(h, i);
}
} else if (h.get(i - 1).compareTo(h.get(getParentIndex(i) - 1)) > 0) {
pushUpMax(h, i);
} else {
swap(i - 1, getParentIndex(i) - 1, h);
i = getParentIndex(i);
pushUpMin(h, i);
}
}
}
public T min() {
if (!isEmpty()) {
return array.get(0);
}
return null;
}
public T max() {
if (!isEmpty()) {
if (indicator == 2) {
return array.get(0);
}
if (indicator == 3) {
return array.get(1);
}
return array.get(1).compareTo(array.get(2)) < 0 ? array.get(2) : array.get(1);
}
return null;
}
public T removeMin() {
T min = min();
if (min != null) {
if (indicator == 2) {
array.remove(indicator--);
return min;
}
array.set(0, array.get(--indicator - 1));
array.remove(indicator - 1);
pushDown(array, 1);
}
return min;
}
public T removeMax() {
T max = max();
if (max != null) {
int maxIndex;
if (indicator == 2) {
maxIndex = 0;
array.remove(--indicator - 1);
return max;
} else if (indicator == 3) {
maxIndex = 1;
array.remove(--indicator - 1);
return max;
} else {
maxIndex = array.get(1).compareTo(array.get(2)) < 0 ? 2 : 1;
}
array.set(maxIndex, array.get(--indicator - 1));
array.remove(indicator - 1);
pushDown(array, maxIndex + 1);
}
return max;
}
}

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data-structures/src/test/java/com/baeldung/minmaxheap/MinMaxHeapUnitTest.java Normal file
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package com.baeldung.minmaxheap;
import org.junit.Assert;
import org.junit.Test;
import java.util.Arrays;
import java.util.List;
public class MinMaxHeapUnitTest {
@Test
public void givenUnOrderedArray_WhenCreateMinMaxHeap_ThenIsEqualWithMinMaxHeapOrdered() {
List<Integer> list = Arrays.asList(34, 12, 28, 9, 30, 19, 1, 40);
MinMaxHeap<Integer> minMaxHeap = new MinMaxHeap<>(list);
minMaxHeap.create();
Assert.assertEquals(Arrays.asList(1, 40, 34, 9, 30, 19, 28, 12), list);
}
@Test
public void givenNewElement_WhenInserted_ThenIsEqualWithMinMaxHeapOrdered() {
MinMaxHeap<Integer> minMaxHeap = new MinMaxHeap(8);
minMaxHeap.insert(34);
minMaxHeap.insert(12);
minMaxHeap.insert(28);
minMaxHeap.insert(9);
minMaxHeap.insert(30);
minMaxHeap.insert(19);
minMaxHeap.insert(1);
minMaxHeap.insert(40);
Assert.assertEquals(Arrays.asList(1, 40, 28, 12, 30, 19, 9, 34), minMaxHeap.getMinMaxHeap());
}
}