1 /* 2 * Copyright 2018 The Android Open Source Project 3 * 4 * Licensed under the Apache License, Version 2.0 (the "License"); 5 * you may not use this file except in compliance with the License. 6 * You may obtain a copy of the License at 7 * 8 * http://www.apache.org/licenses/LICENSE-2.0 9 * 10 * Unless required by applicable law or agreed to in writing, software 11 * distributed under the License is distributed on an "AS IS" BASIS, 12 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. 13 * See the License for the specific language governing permissions and 14 * limitations under the License. 15 */ 16 17 package com.android.tools.build.jetifier.processor 18 19 /** 20 * Creates a cartesian product from the given lists. 21 * 22 * Example: ((1, 2), (a, b)) 23 * Result: ((1, a), (1, b), (2, a), (2,b)) 24 */ 25 fun <T> List<List<T>>.cartesianProduct(): List<List<T>> { 26 return cartesianProductInternal(this.size - 1, this) 27 } 28 29 private fun <T> cartesianProductInternal(index: Int, lists: List<List<T>>): List<MutableList<T>> { 30 val result = mutableListOf<MutableList<T>>() 31 if (index == -1) { 32 result.add(mutableListOf()) 33 } else { 34 for (obj in lists[index]) { 35 for (set in cartesianProductInternal(index - 1, lists)) { 36 set.add(obj) 37 result.add(set) 38 } 39 } 40 } 41 return result 42 }
