From 023487875139e3e8acd52298979b7dd903d70ed5 Mon Sep 17 00:00:00 2001
From: Peter Wu <peter@lekensteyn.nl>
Date: Wed, 1 Apr 2015 09:20:19 +0200
Subject: Rate multi n-grams higher

---
 spellchecker/src/CorpusReader.java | 20 ++++++++++++++++----
 1 file changed, 16 insertions(+), 4 deletions(-)

diff --git a/spellchecker/src/CorpusReader.java b/spellchecker/src/CorpusReader.java
index f815cfd..f9df1ca 100644
--- a/spellchecker/src/CorpusReader.java
+++ b/spellchecker/src/CorpusReader.java
@@ -113,10 +113,22 @@ public class CorpusReader {
             throw new IllegalArgumentException("NGram must be non-empty.");
         }
 
-        double smoothedCount = 0.0;
-
-        // simplest smoothing implementation: plus 1.
-        smoothedCount = getNGramCount(NGram) + 1;
+        double smoothedCount = getNGramCount(NGram);
+
+        int n_words = NGram.split(" ").length + 1;
+        switch (n_words) {
+            case 1: // unigram
+                smoothedCount += 1.0;
+                break;
+            case 2: // bigram
+                smoothedCount += 2.0;
+                break;
+            case 3: // trigram
+                smoothedCount += 4.0;
+                break;
+            default:
+                throw new AssertionError("Unknown n-gram with n=" + n_words);
+        }
 
         return smoothedCount;
     }
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