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A general programming library in Java/Android. It's easy to learn and simple to use with concise and powerful APIs.
/*
* Copyright (c) 2017, Haiyang Li.
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
package com.landawn.abacus.util;
import java.util.Collection;
import java.util.Comparator;
import java.util.Iterator;
import java.util.PriorityQueue;
import java.util.Queue;
import com.landawn.abacus.util.u.Nullable;
import com.landawn.abacus.util.u.OptionalByte;
import com.landawn.abacus.util.u.OptionalChar;
import com.landawn.abacus.util.u.OptionalDouble;
import com.landawn.abacus.util.u.OptionalFloat;
import com.landawn.abacus.util.u.OptionalInt;
import com.landawn.abacus.util.u.OptionalLong;
import com.landawn.abacus.util.u.OptionalShort;
/**
*
* @author Haiyang Li
*/
public final class Median {
private Median() {
// no instance.
}
/**
* Returns a {@code Pair} with {@code left} is the value at the index of {@code (a.length - 1) / 2} when the array is sorted,
* and the {@code right} is the value at the index of {@code a.length / 2} if the length of array is even.
*
* @param a
* @return
* @throws IllegalArgumentException if the specified {@code Array} is null or empty.
* @see #of(int[])
*/
@SafeVarargs
public static Pair of(final char... a) throws IllegalArgumentException {
N.checkArgNotNullOrEmpty(a, "The spcified array 'a' can't be null or empty"); //NOSONAR
return of(a, 0, a.length);
}
/**
* Returns a {@code Pair} with {@code left} is the value at the index of {@code (a.length - 1) / 2} when the array is sorted,
* and the {@code right} is the value at the index of {@code a.length / 2} if the length of array is even.
*
* @param a
* @param fromIndex
* @param toIndex
* @return
* @see #of(int[])
*/
public static Pair of(final char[] a, final int fromIndex, final int toIndex) {
if (N.isNullOrEmpty(a) || toIndex - fromIndex < 1) {
throw new IllegalArgumentException("The length of array can't be null or empty"); //NOSONAR
}
N.checkFromToIndex(fromIndex, toIndex, a.length);
final int len = toIndex - fromIndex;
if (len == 1) {
return Pair.of(a[fromIndex], OptionalChar.empty());
} else if (len == 2) {
return a[fromIndex] <= a[fromIndex + 1] ? Pair.of(a[fromIndex], OptionalChar.of(a[fromIndex + 1]))
: Pair.of(a[fromIndex + 1], OptionalChar.of(a[fromIndex]));
} else if (len == 3) {
return Pair.of(N.median(a, fromIndex, toIndex), OptionalChar.empty());
} else {
final int k = len / 2 + 1;
final Queue queue = new PriorityQueue<>(k);
for (int i = fromIndex; i < toIndex; i++) {
if (queue.size() < k) {
queue.add(a[i]);
} else {
if (a[i] > queue.peek()) {
queue.remove();
queue.add(a[i]);
}
}
}
return len % 2 == 0 ? Pair.of(queue.poll(), OptionalChar.of(queue.poll())) : Pair.of(queue.peek(), OptionalChar.empty());
}
}
/**
* Returns a {@code Pair} with {@code left} is the value at the index of {@code (a.length - 1) / 2} when the array is sorted,
* and the {@code right} is the value at the index of {@code a.length / 2} if the length of array is even.
*
* @param a
* @return
* @throws IllegalArgumentException if the specified {@code Array} is null or empty.
* @see #of(int[])
*/
@SafeVarargs
public static Pair of(final byte... a) throws IllegalArgumentException {
N.checkArgNotNullOrEmpty(a, "The spcified array 'a' can't be null or empty");
return of(a, 0, a.length);
}
/**
* Returns a {@code Pair} with {@code left} is the value at the index of {@code (a.length - 1) / 2} when the array is sorted,
* and the {@code right} is the value at the index of {@code a.length / 2} if the length of array is even.
*
* @param a
* @param fromIndex
* @param toIndex
* @return
* @see #of(int[])
*/
public static Pair of(final byte[] a, final int fromIndex, final int toIndex) {
if (N.isNullOrEmpty(a) || toIndex - fromIndex < 1) {
throw new IllegalArgumentException("The length of array can't be null or empty");
}
N.checkFromToIndex(fromIndex, toIndex, a.length);
final int len = toIndex - fromIndex;
if (len == 1) {
return Pair.of(a[fromIndex], OptionalByte.empty());
} else if (len == 2) {
return a[fromIndex] <= a[fromIndex + 1] ? Pair.of(a[fromIndex], OptionalByte.of(a[fromIndex + 1]))
: Pair.of(a[fromIndex + 1], OptionalByte.of(a[fromIndex]));
} else if (len == 3) {
return Pair.of(N.median(a, fromIndex, toIndex), OptionalByte.empty());
} else {
final int k = len / 2 + 1;
final Queue queue = new PriorityQueue<>(k);
for (int i = fromIndex; i < toIndex; i++) {
if (queue.size() < k) {
queue.add(a[i]);
} else {
if (a[i] > queue.peek()) {
queue.remove();
queue.add(a[i]);
}
}
}
return len % 2 == 0 ? Pair.of(queue.poll(), OptionalByte.of(queue.poll())) : Pair.of(queue.peek(), OptionalByte.empty());
}
}
/**
* Returns a {@code Pair} with {@code left} is the value at the index of {@code (a.length - 1) / 2} when the array is sorted,
* and the {@code right} is the value at the index of {@code a.length / 2} if the length of array is even.
*
* @param a
* @return
* @throws IllegalArgumentException if the specified {@code Array} is null or empty.
* @see #of(int[])
*/
@SafeVarargs
public static Pair of(final short... a) throws IllegalArgumentException {
N.checkArgNotNullOrEmpty(a, "The spcified array 'a' can't be null or empty");
return of(a, 0, a.length);
}
/**
* Returns a {@code Pair} with {@code left} is the value at the index of {@code (a.length - 1) / 2} when the array is sorted,
* and the {@code right} is the value at the index of {@code a.length / 2} if the length of array is even.
*
* @param a
* @param fromIndex
* @param toIndex
* @return
* @see #of(int[])
*/
public static Pair of(final short[] a, final int fromIndex, final int toIndex) {
if (N.isNullOrEmpty(a) || toIndex - fromIndex < 1) {
throw new IllegalArgumentException("The length of array can't be null or empty");
}
N.checkFromToIndex(fromIndex, toIndex, a.length);
final int len = toIndex - fromIndex;
if (len == 1) {
return Pair.of(a[fromIndex], OptionalShort.empty());
} else if (len == 2) {
return a[fromIndex] <= a[fromIndex + 1] ? Pair.of(a[fromIndex], OptionalShort.of(a[fromIndex + 1]))
: Pair.of(a[fromIndex + 1], OptionalShort.of(a[fromIndex]));
} else if (len == 3) {
return Pair.of(N.median(a, fromIndex, toIndex), OptionalShort.empty());
} else {
final int k = len / 2 + 1;
final Queue queue = new PriorityQueue<>(k);
for (int i = fromIndex; i < toIndex; i++) {
if (queue.size() < k) {
queue.add(a[i]);
} else {
if (a[i] > queue.peek()) {
queue.remove();
queue.add(a[i]);
}
}
}
return len % 2 == 0 ? Pair.of(queue.poll(), OptionalShort.of(queue.poll())) : Pair.of(queue.peek(), OptionalShort.empty());
}
}
/**
* Returns a {@code Pair} with {@code left} is the value at the index of {@code (a.length - 1) / 2} when the array is sorted,
* and the {@code right} is the value at the index of {@code a.length / 2} if the length of array is even.
*
* The input array don't need to be sorted. in other words, there is no benefit even if the array is sorted.
*
*
*
*
* Median.of(1); // -> [1, empty]
* Median.of(1, 3); // -> [1, 3]
* Median.of(1, 3, 5); // -> [3, empty]
*
* Median.of(1, 1); // -> [1, 1]
* Median.of(1, 1, 3); // -> [1, empty]
* Median.of(1, 1, 3, 5); // -> [1, 3]
* Median.of(1, 1, 1, 3, 5); // -> [1, empty]
* Median.of(1, 1, 1, 3, 3, 5); // -> [1, 3]
* Median.of(1, 1, 1, 3, 3, 3, 5); // -> [3, empty]
*
*
*
*
* @param a
* @return
* @throws IllegalArgumentException if the specified {@code Array} is null or empty.
*/
@SafeVarargs
public static Pair of(final int... a) throws IllegalArgumentException {
N.checkArgNotNullOrEmpty(a, "The spcified array 'a' can't be null or empty");
return of(a, 0, a.length);
}
/**
* Returns a {@code Pair} with {@code left} is the value at the index of {@code (a.length - 1) / 2} when the array is sorted,
* and the {@code right} is the value at the index of {@code a.length / 2} if the length of array is even.
*
* @param a
* @param fromIndex
* @param toIndex
* @return
* @throws IllegalArgumentException if specified array is empty or length is zero.
*/
public static Pair of(final int[] a, final int fromIndex, final int toIndex) {
if (N.isNullOrEmpty(a) || toIndex - fromIndex < 1) {
throw new IllegalArgumentException("The length of array can't be null or empty");
}
N.checkFromToIndex(fromIndex, toIndex, a.length);
final int len = toIndex - fromIndex;
if (len == 1) {
return Pair.of(a[fromIndex], OptionalInt.empty());
} else if (len == 2) {
return a[fromIndex] <= a[fromIndex + 1] ? Pair.of(a[fromIndex], OptionalInt.of(a[fromIndex + 1]))
: Pair.of(a[fromIndex + 1], OptionalInt.of(a[fromIndex]));
} else if (len == 3) {
return Pair.of(N.median(a, fromIndex, toIndex), OptionalInt.empty());
} else {
final int k = len / 2 + 1;
final Queue queue = new PriorityQueue<>(k);
for (int i = fromIndex; i < toIndex; i++) {
if (queue.size() < k) {
queue.add(a[i]);
} else {
if (a[i] > queue.peek()) {
queue.remove();
queue.add(a[i]);
}
}
}
return len % 2 == 0 ? Pair.of(queue.poll(), OptionalInt.of(queue.poll())) : Pair.of(queue.peek(), OptionalInt.empty());
}
}
/**
* Returns a {@code Pair} with {@code left} is the value at the index of {@code (a.length - 1) / 2} when the array is sorted,
* and the {@code right} is the value at the index of {@code a.length / 2} if the length of array is even.
*
* @param a
* @return
* @throws IllegalArgumentException if the specified {@code Array} is null or empty.
* @see #of(int[])
*/
@SafeVarargs
public static Pair of(final long... a) throws IllegalArgumentException {
N.checkArgNotNullOrEmpty(a, "The spcified array 'a' can't be null or empty");
return of(a, 0, a.length);
}
/**
* Returns a {@code Pair} with {@code left} is the value at the index of {@code (a.length - 1) / 2} when the array is sorted,
* and the {@code right} is the value at the index of {@code a.length / 2} if the length of array is even.
*
* @param a
* @param fromIndex
* @param toIndex
* @return
* @see #of(int[])
*/
public static Pair of(final long[] a, final int fromIndex, final int toIndex) {
if (N.isNullOrEmpty(a) || toIndex - fromIndex < 1) {
throw new IllegalArgumentException("The length of array can't be null or empty");
}
N.checkFromToIndex(fromIndex, toIndex, a.length);
final int len = toIndex - fromIndex;
if (len == 1) {
return Pair.of(a[fromIndex], OptionalLong.empty());
} else if (len == 2) {
return a[fromIndex] <= a[fromIndex + 1] ? Pair.of(a[fromIndex], OptionalLong.of(a[fromIndex + 1]))
: Pair.of(a[fromIndex + 1], OptionalLong.of(a[fromIndex]));
} else if (len == 3) {
return Pair.of(N.median(a, fromIndex, toIndex), OptionalLong.empty());
} else {
final int k = len / 2 + 1;
final Queue queue = new PriorityQueue<>(k);
for (int i = fromIndex; i < toIndex; i++) {
if (queue.size() < k) {
queue.add(a[i]);
} else {
if (a[i] > queue.peek()) {
queue.remove();
queue.add(a[i]);
}
}
}
return len % 2 == 0 ? Pair.of(queue.poll(), OptionalLong.of(queue.poll())) : Pair.of(queue.peek(), OptionalLong.empty());
}
}
/**
* Returns a {@code Pair} with {@code left} is the value at the index of {@code (a.length - 1) / 2} when the array is sorted,
* and the {@code right} is the value at the index of {@code a.length / 2} if the length of array is even.
*
* @param a
* @return
* @throws IllegalArgumentException if the specified {@code Array} is null or empty.
* @see #of(int[])
*/
@SafeVarargs
public static Pair of(final float... a) throws IllegalArgumentException {
N.checkArgNotNullOrEmpty(a, "The spcified array 'a' can't be null or empty");
return of(a, 0, a.length);
}
/**
* Returns a {@code Pair} with {@code left} is the value at the index of {@code (a.length - 1) / 2} when the array is sorted,
* and the {@code right} is the value at the index of {@code a.length / 2} if the length of array is even.
*
* @param a
* @param fromIndex
* @param toIndex
* @return
* @see #of(int[])
*/
public static Pair of(final float[] a, final int fromIndex, final int toIndex) {
if (N.isNullOrEmpty(a) || toIndex - fromIndex < 1) {
throw new IllegalArgumentException("The length of array can't be null or empty");
}
N.checkFromToIndex(fromIndex, toIndex, a.length);
final int len = toIndex - fromIndex;
if (len == 1) {
return Pair.of(a[fromIndex], OptionalFloat.empty());
} else if (len == 2) {
return a[fromIndex] <= a[fromIndex + 1] ? Pair.of(a[fromIndex], OptionalFloat.of(a[fromIndex + 1]))
: Pair.of(a[fromIndex + 1], OptionalFloat.of(a[fromIndex]));
} else if (len == 3) {
return Pair.of(N.median(a, fromIndex, toIndex), OptionalFloat.empty());
} else {
final int k = len / 2 + 1;
final Queue queue = new PriorityQueue<>(k);
for (int i = fromIndex; i < toIndex; i++) {
if (queue.size() < k) {
queue.add(a[i]);
} else {
if (a[i] > queue.peek()) {
queue.remove();
queue.add(a[i]);
}
}
}
return len % 2 == 0 ? Pair.of(queue.poll(), OptionalFloat.of(queue.poll())) : Pair.of(queue.peek(), OptionalFloat.empty());
}
}
/**
* Returns a {@code Pair} with {@code left} is the value at the index of {@code (a.length - 1) / 2} when the array is sorted,
* and the {@code right} is the value at the index of {@code a.length / 2} if the length of array is even.
*
* @param a
* @return
* @throws IllegalArgumentException if the specified {@code Array} is null or empty.
* @see #of(int[])
*/
@SafeVarargs
public static Pair of(final double... a) throws IllegalArgumentException {
N.checkArgNotNullOrEmpty(a, "The spcified array 'a' can't be null or empty");
return of(a, 0, a.length);
}
/**
* Returns a {@code Pair} with {@code left} is the value at the index of {@code (a.length - 1) / 2} when the array is sorted,
* and the {@code right} is the value at the index of {@code a.length / 2} if the length of array is even.
*
* @param a
* @param fromIndex
* @param toIndex
* @return
* @see #of(int[])
*/
public static Pair of(final double[] a, final int fromIndex, final int toIndex) {
if (N.isNullOrEmpty(a) || toIndex - fromIndex < 1) {
throw new IllegalArgumentException("The length of array can't be null or empty");
}
N.checkFromToIndex(fromIndex, toIndex, a.length);
final int len = toIndex - fromIndex;
if (len == 1) {
return Pair.of(a[fromIndex], OptionalDouble.empty());
} else if (len == 2) {
return a[fromIndex] <= a[fromIndex + 1] ? Pair.of(a[fromIndex], OptionalDouble.of(a[fromIndex + 1]))
: Pair.of(a[fromIndex + 1], OptionalDouble.of(a[fromIndex]));
} else if (len == 3) {
return Pair.of(N.median(a, fromIndex, toIndex), OptionalDouble.empty());
} else {
final int k = len / 2 + 1;
final Queue queue = new PriorityQueue<>(k);
for (int i = fromIndex; i < toIndex; i++) {
if (queue.size() < k) {
queue.add(a[i]);
} else {
if (a[i] > queue.peek()) {
queue.remove();
queue.add(a[i]);
}
}
}
return len % 2 == 0 ? Pair.of(queue.poll(), OptionalDouble.of(queue.poll())) : Pair.of(queue.peek(), OptionalDouble.empty());
}
}
/**
* Returns a {@code Pair} with {@code left} is the value at the index of {@code (a.length - 1) / 2} when the array is sorted,
* and the {@code right} is the value at the index of {@code a.length / 2} if the length of array is even.
*
* @param
* @param a
* @return
* @throws IllegalArgumentException if the specified {@code Array} is null or empty.
* @see #of(int[])
*/
public static > Pair> of(final T[] a) throws IllegalArgumentException {
N.checkArgNotNullOrEmpty(a, "The spcified array 'a' can't be null or empty");
return of(a, 0, a.length);
}
/**
* Returns a {@code Pair} with {@code left} is the value at the index of {@code (a.length - 1) / 2} when the array is sorted,
* and the {@code right} is the value at the index of {@code a.length / 2} if the length of array is even.
*
* @param
* @param a
* @param fromIndex
* @param toIndex
* @return
* @see #of(int[])
*/
public static > Pair> of(final T[] a, final int fromIndex, final int toIndex) {
return of(a, fromIndex, toIndex, Comparators.naturalOrder());
}
/**
* Returns a {@code Pair} with {@code left} is the value at the index of {@code (a.length - 1) / 2} when the array is sorted,
* and the {@code right} is the value at the index of {@code a.length / 2} if the length of array is even.
*
* @param
* @param a
* @param cmp
* @return
* @throws IllegalArgumentException if the specified {@code Array} is null or empty.
* @see #of(int[])
*/
public static Pair> of(final T[] a, Comparator cmp) throws IllegalArgumentException {
N.checkArgNotNullOrEmpty(a, "The spcified array 'a' can't be null or empty");
return of(a, 0, a.length, cmp);
}
/**
* Returns a {@code Pair} with {@code left} is the value at the index of {@code (a.length - 1) / 2} when the array is sorted,
* and the {@code right} is the value at the index of {@code a.length / 2} if the length of array is even.
*
* @param
* @param a
* @param fromIndex
* @param toIndex
* @param cmp
* @return
* @see #of(int[])
*/
@SuppressWarnings("rawtypes")
public static Pair> of(final T[] a, final int fromIndex, final int toIndex, Comparator cmp) {
if (N.isNullOrEmpty(a) || toIndex - fromIndex < 1) {
throw new IllegalArgumentException("The length of array can't be null or empty");
}
N.checkFromToIndex(fromIndex, toIndex, a.length);
cmp = cmp == null ? (Comparator) Comparators.naturalOrder() : cmp;
final int len = toIndex - fromIndex;
if (len == 1) {
return Pair.of(a[fromIndex], Nullable. empty());
} else if (len == 2) {
return N.compare(a[fromIndex], a[fromIndex + 1], cmp) <= 0 ? Pair.of(a[fromIndex], Nullable.of(a[fromIndex + 1]))
: Pair.of(a[fromIndex + 1], Nullable.of(a[fromIndex]));
} else if (len == 3) {
return Pair.of(N.median(a, fromIndex, toIndex, cmp), Nullable. empty());
} else {
final int k = len / 2 + 1;
final Queue queue = new PriorityQueue<>(k, cmp);
for (int i = fromIndex; i < toIndex; i++) {
if (queue.size() < k) {
queue.add(a[i]);
} else {
if (N.compare(a[i], queue.peek(), cmp) > 0) {
queue.remove();
queue.add(a[i]);
}
}
}
return len % 2 == 0 ? Pair.of(queue.poll(), Nullable.of(queue.poll())) : Pair.of(queue.peek(), Nullable. empty());
}
}
/**
*
* @param
* @param c
* @return
*/
public static > Pair> of(final Collection c) {
return of(c, Comparators.naturalOrder());
}
/**
*
* @param
* @param c
* @param cmp
* @return
*/
@SuppressWarnings("rawtypes")
public static Pair> of(final Collection c, Comparator cmp) {
if (N.isNullOrEmpty(c)) {
throw new IllegalArgumentException("The size of collection can't be null or empty");
}
cmp = cmp == null ? (Comparator) Comparators.naturalOrder() : cmp;
final int len = c.size();
if (len == 1) {
return Pair.of(c.iterator().next(), Nullable. empty());
} else if (len == 2) {
final Iterator iter = c.iterator();
final T first = iter.next();
final T second = iter.next();
return N.compare(first, second, cmp) <= 0 ? Pair.of(first, Nullable.of(second)) : Pair.of(second, Nullable.of(first));
} else if (len == 3) {
return Pair.of(N.median(c, cmp), Nullable. empty());
} else {
final int k = len / 2 + 1;
final Queue queue = new PriorityQueue<>(k, cmp);
for (T e : c) {
if (queue.size() < k) {
queue.add(e);
} else {
if (N.compare(e, queue.peek(), cmp) > 0) {
queue.remove();
queue.add(e);
}
}
}
return len % 2 == 0 ? Pair.of(queue.poll(), Nullable.of(queue.poll())) : Pair.of(queue.peek(), Nullable. empty());
}
}
}