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-rw-r--r--src/algorithms/searching/InterpolationSearch.java100
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diff --git a/src/algorithms/searching/InterpolationSearch.java b/src/algorithms/searching/InterpolationSearch.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.*;
+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
+}
+