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Diffstat (limited to 'src/algorithms/searching')
| -rw-r--r-- | src/algorithms/searching/InterpolationSearch.java | 100 |
1 files changed, 100 insertions, 0 deletions
diff --git a/src/algorithms/searching/InterpolationSearch.java b/src/algorithms/searching/InterpolationSearch.java new file mode 100644 index 0000000..1e4aaa8 --- /dev/null +++ b/src/algorithms/searching/InterpolationSearch.java @@ -0,0 +1,100 @@ +/** + * 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.*; +import java.math.*; + + +/** + * Interpolation search class. Interpolation search runs in logarithmic + * time, in average, and linear time in worst case, which will occur with + * rough distrubitions, constant memory, and requires the list to be sorted + * and numerical. Interpolation search often out preforms binary search for + * smoothing distributions. Identity search is not possible, only equality + * search.<br> + * The list must be sorted in ascending order. + */ +public class InterpolationSearch +{ +£>for T in char byte short int long float double; do + /** + * Find the easiest to find occurance of an item in a list + * + * @param item The item to find + * @param array The list in which to search + * @return The index of the easiest to find occurance of the item. The bitwise + * negation of the position it insert it in is returned if it was not found. + */ + public static int indexOf(£{T} item, £{T}[] array) + { + £{T} low, high, at; + int min = 0, mid; + int max = array.length - 1; + + for (;;) + { + if ((low = array[min]) > item) break; + if ((high = array[max]) < item) break; + + if ((at = array[mid = min + (int)((item - low) * (max - min) / (high - low))]) < item) + min = mid + 1; + else if (at > item) + max = mid - 1; + else + return mid; + } + + return (array[min] == item) ? min : ~min; + } +£>done + +£>for T in BigInteger BigDecimal; do + /** + * Find the easiest to find occurance of an item in a list + * + * @param item The item to find + * @param array The list in which to search + * @return The index of the easiest to find occurance of the item. The bitwise + * negation of the position it insert it in is returned if it was not found. + */ + public static int indexOf(£{T} item, £{T}[] array) + { + £{T} low, high, at; + int min = 0, mid; + int max = array.length - 1; + + for (;;) + { + if ((low = array[min]).compareTo(item) > 0) break; + if ((high = array[max]).compareTo(item) < 0) break; + + mid = item.subtract(low).multiply(£{T}.valueOf(max - min)).divide(high.subtract(low)).intValue(); + + if ((at = array[mid += min]).compareTo(item) < 0) + min = mid + 1; + else if (at.compareTo(item) > 0) + max = mid - 1; + else + return mid; + } + + return (array[min] == item) ? min : ~min; + } +£>done +} + |