m + add hybrid interpolation search

Signed-off-by: Mattias Andrée <maandree@operamail.com>

1 files changed, 141 insertions, 0 deletions

diff --git a/src/algorithms/searching/HybridInterpolationSearch.java b/src/algorithms/searching/HybridInterpolationSearch.java
new file mode 100644
index 0000000..888c028
--- /dev/null
+++ b/src/algorithms/searching/HybridInterpolationSearch.java
@@ -0,0 +1,141 @@
+/**
+ * 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.*;
+
+
+/**
+ * Hybrid 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. Hybrid interpolation search uses interpolation
+ * search and falls back to linear search when the number of elemetns left are
+ * small enough. Identity search is not possible, only equality search.<br>
+ * The list must be sorted in ascending order.
+ */
+public class HybridInterpolationSearch
+{
+£>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
+     * @param   fallback  The number of elements at when to fall back to linear 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, int fallback)
+    {
+	£{T} low, high, at;
+	int min = 0, mid;
+	int max = array.length - 1;
+	
+	for (;;)
+	{
+            if (min + fallback >= max)
+                return linearFirst(item, array, min, max);
+            
+	    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
+     * @param   fallback  The number of elements at when to fall back to linear 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, int fallback)
+    {
+        £{T} low, high, at;
+        int min = 0, mid;
+        int max = array.length - 1;
+	
+        for (;;)
+	{
+            if (min + fallback >= max)
+                return linearFirst(item, array, min, max);
+            
+	    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
+
+£>for T in char byte short int long float double Object; do . src/comparable
+    /**
+     * 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 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 (£(equal array[i] item))
+		return i;
+            
+	    i++;
+	}
+	
+        return -1;
+    }
+£>done
+}
+