From aed75adb5b127e5943dd16b0e37a4d9b00d2ac12 Mon Sep 17 00:00:00 2001
From: Peter Wu <peter@lekensteyn.nl>
Date: Sat, 4 Apr 2015 11:06:32 +0200
Subject: Save readonly state across calls

Can be cleaned up a bit... but functionality first now.
---
 spellchecker/src/SpellCorrector.java | 84 ++++++++++++++++++++++++------------
 1 file changed, 56 insertions(+), 28 deletions(-)

diff --git a/spellchecker/src/SpellCorrector.java b/spellchecker/src/SpellCorrector.java
index e3f2955..0bc5b41 100644
--- a/spellchecker/src/SpellCorrector.java
+++ b/spellchecker/src/SpellCorrector.java
@@ -1,6 +1,8 @@
 
 import java.util.HashMap;
+import java.util.HashSet;
 import java.util.Map;
+import java.util.Set;
 
 public class SpellCorrector {
 
@@ -37,51 +39,77 @@ public class SpellCorrector {
         this.cmr = cmr;
     }
 
+    /**
+     * Converts a set of word indices which were modified to an array of length
+     * {@code n} of which elements are set to true when those should not be
+     * modified.
+     */
+    private boolean[] getReadonlyIndices(int n, Set<Integer> modifiedIndices) {
+        boolean[] words_readonly = new boolean[n];
+        for (Integer index : modifiedIndices) {
+            if (index > 0) {
+                words_readonly[index - 1] = true;
+            }
+            words_readonly[index] = true;
+            if (index + 1 < n) {
+                words_readonly[index + 1] = true;
+            }
+        }
+        return words_readonly;
+    }
+
     /**
      * Tries to find up to {@code maxTypos} number of misspelled words.
      *
-     * @param maxTypos The maximum number of look erroneous words for.
      * @return The resulting rater containing probabilities and the corrected
      * sentence or null if no suggestions are found.
      */
-    private SentenceRater findCorrected(String[] words, int maxTypos) {
-        SentenceRater rater = new SentenceRater(words);
-
+    private SentenceRater findBetterWord(String[] words,
+            Set<Integer> modifiedIndices) {
+        SentenceRater bestResult = null;
         // find best word
         for (int i = 0; i < words.length; i++) {
             final int word_index = i;
             String old_word = words[word_index];
+            SentenceRater rater = new SentenceRater(words,
+                    getReadonlyIndices(words.length, modifiedIndices));
+
             // try to find a better suggestion for this word.
             Map<String, Double> candidates = getCandidateWords(old_word);
             candidates.forEach((word, channel_probability) -> {
                 rater.tryWord(word_index, word, channel_probability);
             });
-        };
 
-        // if a better word was found, use the change
-        if (rater.hasBetterSuggestion()) {
-            rater.saveSuggestion();
-            // If some other errors are still possible, hunt for those!
-            if (maxTypos > 1) {
-                SentenceRater subResult;
-                subResult = findCorrected(rater.getBestSentence(), maxTypos - 1);
-                // Did it find a corrected word?
-                if (subResult != null) {
-                    // Yes it did. Is this the best one so far?
-                    if (subResult.getBestScore() > rater.getBestScore()) {
-                        System.err.println("Subresult is better!");
-                        return subResult;
+            // if a better word was found, use the change
+            if (rater.hasBetterSuggestion()) {
+                rater.saveSuggestion();
+                bestResult = rater;
+
+                // If some other errors are still possible, hunt for those!
+                modifiedIndices.add(i);
+                if (modifiedIndices.size() < MAX_TYPOS) {
+                    SentenceRater subResult;
+                    subResult = findBetterWord(rater.getBestSentence(), modifiedIndices);
+                    // Did it find a corrected word?
+                    if (subResult != null) {
+                        // Yes it did. Is this the best one so far?
+                        if (subResult.getBestScore() > rater.getBestScore()) {
+                            System.err.println("Subresult is better!");
+                            bestResult = subResult;
+                        } else {
+                            System.err.println("Subresult is not better!");
+                        }
+                    } else {
+                        System.err.println("no subresult found");
                     }
-                    System.err.println("Subresult is not better!");
-                } else {
-                    System.err.println("no subresult found");
                 }
+                // make the context to be editable again
+                modifiedIndices.remove(i);
+            } else {
+                System.err.println("No suggestion found for " + old_word + ".");
             }
-            return rater;
-        } else {
-            System.err.println("No suggestion found.");
-            return null;
         }
+        return bestResult;
     }
 
     public String correctPhrase(String phrase) {
@@ -91,7 +119,7 @@ public class SpellCorrector {
 
         String[] words = phrase.split(" ");
 
-        SentenceRater rater = findCorrected(words, MAX_TYPOS);
+        SentenceRater rater = findBetterWord(words, new HashSet<>());
         // if a better sentence is found, use it.
         if (rater != null) {
             words = rater.getBestSentence();
@@ -241,10 +269,10 @@ public class SpellCorrector {
         private double sentence_probability;
         private WordModification best_modification;
 
-        public SentenceRater(String[] words) {
+        public SentenceRater(String[] words, boolean[] word_readonly) {
             this.words = words.clone();
             this.word_likelihoods = new double[words.length];
-            this.words_readonly = new boolean[words.length];
+            this.words_readonly = word_readonly;
             for (int i = 0; i < words.length; i++) {
                 word_likelihoods[i] = getWordLikelihood(i,
                         LM_PROBABILITY_UNMODIFIED);
-- 
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