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| -rw-r--r-- | src/algorithms/searching/LinearSearch.java | 260 |
1 files changed, 260 insertions, 0 deletions
diff --git a/src/algorithms/searching/LinearSearch.java b/src/algorithms/searching/LinearSearch.java new file mode 100644 index 0000000..0e621b7 --- /dev/null +++ b/src/algorithms/searching/LinearSearch.java @@ -0,0 +1,260 @@ +/** + * Copyright © 2014 Mattias Andrée (maandree@member.fsf.org) + * + * This program is free software: you can redistribute it and/or modify + * it under the terms of the GNU Affero General Public License as published by + * the Free Software Foundation, either version 3 of the License, or + * (at your option) any later version. + * + * This program is distributed in the hope that it will be useful, + * but WITHOUT ANY WARRANTY; without even the implied warranty of + * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the + * GNU Affero General Public License for more details. + * + * You should have received a copy of the GNU Affero General Public License + * along with this program. If not, see <http://www.gnu.org/licenses/>. + */ +package algorithms.searching; + +import java.util.*; + + +/** + * Linear search class. Linear search runs in linear time, constant memory, + * and imposes no requirements on the list. Linear is not recommended for + * sorted lists. + */ +public class LinearSearch +{ + /** + * The value returned if the item was not found + */ + public static final int NOT_FOUND = -1; + + + + /** + * Finds the index of the first occurance of an item in a list + * + * @param item The item for which to search + * @param array The list in which to search + * @return The index of the first occurance of the item within the list, {@link #NOT_FOUND} if it was not found + */ + public static int indexOfFirstEqual(Object item, Object[] array) + { + return indexOfFirstEqual(item, array, 0, -1); + } + + /** + * Finds the index of the first occurance of an item in a list + * + * @param item The item for which to search + * @param array The list in which to search + * @param start Offset for the list or search range + * @return The index of the first occurance of the item within the list, {@link #NOT_FOUND} if it was not found + */ + public static int indexOfFirstEqual(Object item, Object[] array, int start) + { + return indexOfFirstEqual(item, array, start, -1); + } + + /** + * Finds the index of the first occurance of an item in a list + * + * @param item The item for which to search + * @param array The list in which to search + * @param start Offset for the list or search range + * @param end End of the list or search range + * @return The index of the first occurance of the item within the list, {@link #NOT_FOUND} if it was not found + */ + public static int indexOfFirstEqual(Object item, Object[] array, int start, int end) + { + int i = start < 0 ? (array.length - start) : start; + int n = end < 0 ? (array.length - end) : end; + + for (;;) + { + if (i == n) + break; + + if ((array[i] == null) == (item == null)) + { + if (item == null) + return i; + if (array[i].equals(item)) + return i; + } + + i++; + } + + return NOT_FOUND; + } + + /** + * Finds the index of the last occurance of an item in a list + * + * @param item The item for which to search + * @param array The list in which to search + * @return The index of the last occurance of the item within the list, {@link #NOT_FOUND} if it was not found + */ + public static int indexOfLastEqual(Object item, Object[] array) + { + return indexOfLastEqual(item, array, -1, 0); + } + + /** + * Finds the index of the last occurance of an item in a list + * + * @param item The item for which to search + * @param array The list in which to search + * @param start End offset for the list or search range + * @return The index of the last occurance of the item within the list, {@link #NOT_FOUND} if it was not found + */ + public static int indexOfLastEqual(Object item, Object[] array, int start) + { + return indexOfLastEqual(item, array, start, 0); + } + + /** + * Finds the index of the last occurance of an item in a list + * + * @param item The item for which to search + * @param array The list in which to search + * @param start End offset for the list or search range + * @param end Beginning offset for the list or search range + * @return The index of the last occurance of the item within the list, {@link #NOT_FOUND} if it was not found + */ + public static int indexOfLastEqual(Object item, Object[] array, int start, int end) + { + int i = start < 0 ? (array.length - start) : start; + int n = end < 0 ? (array.length - end) : end; + + for (;;) + { + if (i == n) + break; + + if ((array[i] == null) == (item == null)) + { + if (item == null) + return i; + if (array[i].equals(item)) + return i; + } + + i--; + } + + return NOT_FOUND; + } + +£>for T in boolean char byte short int long float double Object; do + /** + * Finds the index of the first occurance of an item in a list + * + * @param item The item for which to search + * @param array The list in which to search + * @return The index of the first occurance of the item within the list, {@link #NOT_FOUND} if it was not found + */ + public static int indexOfFirst(£{T} item, £{T}[] array) + { + return indexOfFirst(item, array, 0, -1); + } + + /** + * Finds the index of the first occurance of an item in a list + * + * @param item The item for which to search + * @param array The list in which to search + * @param start Offset for the list or search range + * @return The index of the first occurance of the item within the list, {@link #NOT_FOUND} if it was not found + */ + public static int indexOfFirst(£{T} item, £{T}[] array, int start) + { + return indexOfFirst(item, array, start, -1); + } + + /** + * Finds the index of the first occurance of an item in a list + * + * @param item The item for which to search + * @param array The list in which to search + * @param start Offset for the list or search range + * @param end End of the list or search range + * @return The index of the first occurance of the item within the list, {@link #NOT_FOUND} if it was not found + */ + public static int indexOfFirst(£{T} item, £{T}[] array, int start, int end) + { + int i = start < 0 ? (array.length - start) : start; + int n = end < 0 ? (array.length - end) : end; + + for (;;) + { + if (i == n) + break; + + if (array[i] == item) + return i; + + i++; + } + + return NOT_FOUND; + } + + /** + * Finds the index of the last occurance of an item in a list + * + * @param item The item for which to search + * @param array The list in which to search + * @return The index of the last occurance of the item within the list, {@link #NOT_FOUND} if it was not found + */ + public static int indexOfLast(£{T} item, £{T}[] array) + { + return indexOfLast(item, array, -1, 0); + } + + /** + * Finds the index of the last occurance of an item in a list + * + * @param item The item for which to search + * @param array The list in which to search + * @param start End offset for the list or search range + * @return The index of the last occurance of the item within the list, {@link #NOT_FOUND} if it was not found + */ + public static int indexOfLast(£{T} item, £{T}[] array, int start) + { + return indexOfLast(item, array, start, 0); + } + + /** + * Finds the index of the last occurance of an item in a list + * + * @param item The item for which to search + * @param array The list in which to search + * @param start End offset for the list or search range + * @param end Beginning offset for the list or search range + * @return The index of the last occurance of the item within the list, {@link #NOT_FOUND} if it was not found + */ + public static int indexOfLast(£{T} item, £{T}[] array, int start, int end) + { + int i = start < 0 ? (array.length - start) : start; + int n = end < 0 ? (array.length - end) : end; + + for (;;) + { + if (i == n) + break; + + if (array[i] == item) + return i; + + i--; + } + + return NOT_FOUND; + } +£>done +} + |