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/*
* Copyright (C) 2012 The Guava Authors
*
* 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.google.common.collect;
import static com.google.common.base.Preconditions.checkElementIndex;
import com.google.common.annotations.GwtCompatible;
import com.google.common.math.IntMath;
import java.util.AbstractList;
import java.util.List;
import java.util.ListIterator;
import java.util.RandomAccess;
import org.checkerframework.checker.nullness.qual.Nullable;
/**
* Implementation of {@link Lists#cartesianProduct(List)}.
*
* @author Louis Wasserman
*/
@GwtCompatible
final class CartesianList<E> extends AbstractList<List<E>> implements RandomAccess {
private final transient ImmutableList<List<E>> axes;
private final transient int[] axesSizeProduct;
static <E> List<List<E>> create(List<? extends List<? extends E>> lists) {
ImmutableList.Builder<List<E>> axesBuilder = new ImmutableList.Builder<>(lists.size());
for (List<? extends E> list : lists) {
List<E> copy = ImmutableList.copyOf(list);
if (copy.isEmpty()) {
return ImmutableList.of();
}
axesBuilder.add(copy);
}
return new CartesianList<E>(axesBuilder.build());
}
CartesianList(ImmutableList<List<E>> axes) {
this.axes = axes;
int[] axesSizeProduct = new int[axes.size() + 1];
axesSizeProduct[axes.size()] = 1;
try {
for (int i = axes.size() - 1; i >= 0; i--) {
axesSizeProduct[i] = IntMath.checkedMultiply(axesSizeProduct[i + 1], axes.get(i).size());
}
} catch (ArithmeticException e) {
throw new IllegalArgumentException(
"Cartesian product too large; must have size at most Integer.MAX_VALUE");
}
this.axesSizeProduct = axesSizeProduct;
}
private int getAxisIndexForProductIndex(int index, int axis) {
return (index / axesSizeProduct[axis + 1]) % axes.get(axis).size();
}
@Override
public int indexOf(Object o) {
if (!(o instanceof List)) {
return -1;
}
List<?> list = (List<?>) o;
if (list.size() != axes.size()) {
return -1;
}
ListIterator<?> itr = list.listIterator();
int computedIndex = 0;
while (itr.hasNext()) {
int axisIndex = itr.nextIndex();
int elemIndex = axes.get(axisIndex).indexOf(itr.next());
if (elemIndex == -1) {
return -1;
}
computedIndex += elemIndex * axesSizeProduct[axisIndex + 1];
}
return computedIndex;
}
@Override
public ImmutableList<E> get(final int index) {
checkElementIndex(index, size());
return new ImmutableList<E>() {
@Override
public int size() {
return axes.size();
}
@Override
public E get(int axis) {
checkElementIndex(axis, size());
int axisIndex = getAxisIndexForProductIndex(index, axis);
return axes.get(axis).get(axisIndex);
}
@Override
boolean isPartialView() {
return true;
}
};
}
@Override
public int size() {
return axesSizeProduct[0];
}
@Override
public boolean contains(@Nullable Object o) {
return indexOf(o) != -1;
}
}
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