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-rw-r--r--src/algorithms/searching/HybridBinarySearch.java297
1 files changed, 297 insertions, 0 deletions
diff --git a/src/algorithms/searching/HybridBinarySearch.java b/src/algorithms/searching/HybridBinarySearch.java
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+/**
+ * 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.*;
+
+
+/**
+ * Hybrid binary search class. Binary search runs in logarithmic time, constant
+ * memory, and requires the list to be sorted. Binary search often out preforms
+ * linear search, interpolation sort however often out preforms binary search
+ * for lists with smooth distribution. Hybrid binary search uses binary search
+ * and falls back to linear search when the number of elemetns left are small
+ * enough. Identity search is not possible, only equality search. Null elements
+ * are not allowed, unless the specified compator allows it.
+ */
+public class HybridBinarySearch
+{
+ /**
+ * All elements in the array is the searched for item
+ */
+ public static final int EVERY_ELEMENT = -1;
+
+ /**
+ * Item was not on the edges, but may be inside
+ * Values lower than this value indicate that the value does
+ * not exist.
+ */
+ public static final int MAYBE = -2;
+
+ /**
+ * The item's value is smaller than the smallest in the array.
+ * This value and lower values indicate that the value does
+ * not exist.
+ */
+ public static final int TOO_SMALL = -3;
+
+ /**
+ * The item's value is larger than the largest in the array
+ */
+ public static final int TOO_LARGE = -4;
+
+
+
+ /**
+ * List sort order
+ */
+ public static enum SortOrder
+ {
+ /**
+ * Bigger index, bigger value
+ */
+ ASCENDING,
+
+ /**
+ * Bigger index, smaller value
+ */
+ DESCENDING,
+
+ }
+
+ /**
+ * List sort order
+ */
+ public static enum SearchMode
+ {
+ /**
+ * Look for the index of the easiest to find occurence
+ */
+ FIND_ANY,
+
+ /**
+ * Look for the index of the first occurence
+ */
+ FIND_FIRST,
+
+ /**
+ * Look for the index of the last occurence
+ */
+ FIND_LAST,
+
+ /**
+ * Look for both the index of the fist occurence and of the last occurence.<br>
+ * The returned value will be {@code (LAST << 32) | FIRST}.
+ */
+ FIND_FIST_AND_LAST,
+
+ }
+
+
+
+£>for T in boolean char byte short int long float double T T++; do . src/comparable
+
+ /**
+ * Gets whether an item may be contained by a list
+ *
+ * @param item The item for which to search
+ * @param array The list in which to search
+ * @param order The list's element order
+ * @return {@link #MAYBE}, {@link #TOO_SMALL}, {@link #TOO_LARGE}, {@link #EVERY_ELEMENT}
+ * or the index of a(!) found item [first or last position]
+ */
+ public static £(fun "int" contains "${T} item, ${Tarray} array, SortOrder order")
+ {
+ /* This is identical to as in BinarySearch */
+
+ int low = £(cmp "array[0]" "item");
+
+ if (order == SortOrder.ASCENDING)
+ {
+ if (low > 0)
+ return TOO_SMALL;
+
+ int high = £(cmp "array[1]" "item");
+
+ if (low == 0)
+ return high == 0 ? EVERY_ELEMENT : 0;
+
+ return high == 0 ? array.length - 1 : high < 0 ? TOO_LARGE : MAYBE;
+ }
+
+ {
+ if (low < 0)
+ return TOO_SMALL;
+
+ int n = array.length - 1;
+ int high = £(cmp "array[n]" "item");
+
+ if (low == 0)
+ return high == 0 ? EVERY_ELEMENT : 0;
+
+ return high == 0 ? n : high > 0 ? TOO_LARGE : MAYBE;
+ }
+ }
+
+
+ /**
+ * Finds the index of the first occurance of an item in a list
+ *
+ * @param item The item for which to search
+ * @param array The list in which to search
+ * @param start Offset for the list or search range
+ * @param end End of the list or search range
+ * @return The index of the first occurance of the item within the list, {@code -1} if it was not found
+ */
+ private static £(fun "int" linearFirst "${T} item, ${T}[] array, int start, int end")
+ {
+ /* This is nearly identical to LinearSearch.indexOfFirst */
+
+ int i = start < 0 ? (array.length - start) : start;
+ int n = end < 0 ? (array.length - end) : end;
+
+ for (;;)
+ {
+ if (i == n)
+ break;
+
+ if (array[i] == item)
+ return i;
+
+ i++;
+ }
+
+ return -1;
+ }
+
+ /**
+ * Finds the first, last or any occurance of an item in a list
+ *
+ * @param item The item for which to search
+ * @param array The list in which to search
+ * @param order The list's element order
+ * @param mode The search mode
+ * @param fallback The number of elements at when to fall back to linear search
+ * @return The index of the found item, if not mode does not say otherwise, or, if not
+ * found, the bitwise negation of the position to which it should be inserted
+ */
+ public static £(fun "long" indexOf "${T} item, ${Tarray} array, SortOrder order, SearchMode mode, int fallback")
+ {
+ £{Telement} x;
+
+ int min = 0, mid, rc = -1;
+ int max = array.length - 1;
+
+£>function f
+£>{
+ if (mode == SearchMode.£{1})
+ for (;;)
+ {
+ if (min + fallback >= max)
+ return linearFirst(item, array, min, max);
+
+ if (item == (x = array[mid = (min + max) >>> 1]))
+ £{2};
+
+ /* NB! (x R item), instead of (item R x) */
+ if (£(${3} x item)) min = mid + 1;
+ else max = mid - 1;
+
+ if (min > max)
+ return £{4};
+ }
+£>}
+
+£>function p
+£>{
+ for (;;)
+ {
+£>if [ $3 = 0 ]; then
+ if (min + fallback >= max)
+ {
+ first = last = rc = linearFirst(item, array, min, max);
+ easyMin = first + 1;
+ easyMax = max;
+ normal = true;
+ if (last >= 0)
+ break;
+ }
+£>else
+ if (!normal && (min + fallback >= max))
+ {
+ first = last = rc = linearFirst(item, array, min, max);
+ normal = true;
+ if (last >= 0)
+ {
+ easyMin = first + 1;
+ easyMax = max;
+ break;
+ }
+ }
+£>fi
+
+ if (item == (x = array[mid = (min + max) >>> 1]))
+ {
+ rc = mid;
+£>if [ $3 = 0 ]; then
+ if (easyMin == -1)
+ {
+ easyMax = mid - 1;
+ easyMin = min;
+ }
+£>fi
+ }
+
+ /* NB! (x R item), instead of (item R x) */
+ if (£(${1} x item)) min = mid + 1;
+ else max = mid - 1;
+
+ if (min > max)
+ {
+ if (rc < 0)
+ return ~((long)min);
+ £{2} = rc;
+ break;
+ }
+ }
+
+£>}
+
+£>function _
+£>{
+ {
+£>f FIND_ANY 'return (long)mid' "${1}" '~((long)min)'
+£>f FIND_FIRST 'rc = mid' "${1}" 'rc < 0 ? ~((long)min) : (long)rc'
+£>f FIND_LAST 'rc = mid' "${1}=" 'rc < 0 ? ~((long)min) : (long)rc'
+
+ int easyMin = -1, easyMax = -1, first, last;
+ boolean normal = false;
+£>p "${1}" first 0
+ min = easyMin;
+ max = easyMax;
+£>p "${1}=" last 1
+ return (((long)last) << 32) | (long)first;
+ }
+£>}
+
+ if (order == SortOrder.ASCENDING)
+£>_ 'less'
+£>_ 'greater'
+ }
+£>done
+}
+
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