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Merge pull request #8236 from priyank-sriv/bael-3483 

BAEL-3483 Median of Stream of Integers
This commit is contained in:
Erik Pragt 2019-12-22 17:27:26 +11:00 committed by GitHub
parent f7f100e040 123551a02b
commit 5508f6f43e
3 changed files with 119 additions and 0 deletions
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42
algorithms-miscellaneous-5/src/main/java/com/baeldung/algorithms/integerstreammedian/MedianOfIntegerStream.java Normal file
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package com.baeldung.algorithms.integerstreammedian;
import java.util.PriorityQueue;
import java.util.Queue;
import static java.util.Comparator.reverseOrder;
public class MedianOfIntegerStream {
private Queue<Integer> minHeap, maxHeap;
MedianOfIntegerStream() {
minHeap = new PriorityQueue<>();
maxHeap = new PriorityQueue<>(reverseOrder());
}
void add(int num) {
if (!minHeap.isEmpty() && num < minHeap.peek()) {
maxHeap.offer(num);
if (maxHeap.size() > minHeap.size() + 1) {
minHeap.offer(maxHeap.poll());
}
} else {
minHeap.offer(num);
if (minHeap.size() > maxHeap.size() + 1) {
maxHeap.offer(minHeap.poll());
}
}
}
double getMedian() {
int median;
if (minHeap.size() < maxHeap.size()) {
median = maxHeap.peek();
} else if (minHeap.size() > maxHeap.size()) {
median = minHeap.peek();
} else {
median = (minHeap.peek() + maxHeap.peek()) / 2;
}
return median;
}
}

36
algorithms-miscellaneous-5/src/main/java/com/baeldung/algorithms/integerstreammedian/MedianOfIntegerStream2.java Normal file
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package com.baeldung.algorithms.integerstreammedian;
import java.util.PriorityQueue;
import java.util.Queue;
import static java.util.Comparator.reverseOrder;
public class MedianOfIntegerStream2 {
private Queue<Integer> minHeap, maxHeap;
MedianOfIntegerStream2() {
minHeap = new PriorityQueue<>();
maxHeap = new PriorityQueue<>(reverseOrder());
}
void add(int num) {
if (minHeap.size() == maxHeap.size()) {
maxHeap.offer(num);
minHeap.offer(maxHeap.poll());
} else {
minHeap.offer(num);
maxHeap.offer(minHeap.poll());
}
}
double getMedian() {
int median;
if (minHeap.size() > maxHeap.size()) {
median = minHeap.peek();
} else {
median = (minHeap.peek() + maxHeap.peek()) / 2;
}
return median;
}
}

41
algorithms-miscellaneous-5/src/test/java/com/baeldung/algorithms/integerstreammedian/MedianOfIntegerStreamUnitTest.java Normal file
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package com.baeldung.algorithms.integerstreammedian;
import org.junit.Test;
import java.util.LinkedHashMap;
import java.util.Map;
import static org.junit.Assert.assertEquals;
public class MedianOfIntegerStreamUnitTest {
@Test
public void givenStreamOfIntegers_whenAnElementIsRead_thenMedianChangesWithApproach1() {
MedianOfIntegerStream mis = new MedianOfIntegerStream();
for (Map.Entry<Integer, Double> e : testcaseFixture().entrySet()) {
mis.add(e.getKey());
assertEquals(e.getValue(), (Double) mis.getMedian());
}
}
@Test
public void givenStreamOfIntegers_whenAnElementIsRead_thenMedianChangesWithApproach2() {
MedianOfIntegerStream2 mis = new MedianOfIntegerStream2();
for (Map.Entry<Integer, Double> e : testcaseFixture().entrySet()) {
mis.add(e.getKey());
assertEquals(e.getValue(), (Double) mis.getMedian());
}
}
private Map<Integer, Double> testcaseFixture() {
return new LinkedHashMap<Integer, Double>() {{
put(1, 1d);
put(7, 4d);
put(5, 5d);
put(8, 6d);
put(3, 5d);
put(9, 6d);
put(4, 5d);
}};
}
}