#5960 Add utility for computing "edit distance" between two strings.

ApplicationCode/Application/Tools/RiaStdStringTools.cpp

@@ -142,3 +142,51 @@ size_t RiaStdStringTools::findCharMatchCount( const std::string& s, char c )
     }
     return count;
 }
+
+//--------------------------------------------------------------------------------------------------
+/// Function to find Levenshtein Distance between two strings (x and y).
+/// Adapted from pseudocode from wikipedia: https://en.wikipedia.org/wiki/Levenshtein_distance
+/// Implementation is the Wagner-Fischer variant: https://en.wikipedia.org/wiki/Wagner-Fischer_algorithm
+///
+/// Return value is higher when strings are more "different", and zero when strings are equal.
+//--------------------------------------------------------------------------------------------------
+int RiaStdStringTools::computeEditDistance( const std::string& x, const std::string& y )
+{
+    // for all i and j, T[i,j] will hold the Levenshtein distance between
+    // the first i characters of x and the first j characters of y
+    int m = x.length();
+    int n = y.length();
+
+    std::vector<std::vector<int>> T( m + 1, std::vector<int>( n + 1, 0 ) );
+
+    // source prefixes can be transformed into empty string by
+    // dropping all characters
+    for ( int i = 1; i <= m; i++ )
+        T[i][0] = i;
+
+    // target prefixes can be reached from empty source prefix
+    // by inserting every character
+    for ( int j = 1; j <= n; j++ )
+        T[0][j] = j;
+
+    // fill the lookup table in bottom-up manner
+    for ( int i = 1; i <= m; i++ )
+    {
+        for ( int j = 1; j <= n; j++ )
+        {
+            int substitutionCost;
+            if ( x[i - 1] == y[j - 1] )
+                substitutionCost = 0;
+            else
+                substitutionCost = 1;
+
+            int deletion    = T[i - 1][j] + 1;
+            int insertion   = T[i][j - 1] + 1;
+            int replacement = T[i - 1][j - 1] + substitutionCost;
+            T[i][j]         = std::min( std::min( deletion, insertion ), replacement );
+        }
+    }
+
+    // The distance between the two full strings as the last value computed.
+    return T[m][n];
+}

ApplicationCode/Application/Tools/RiaStdStringTools.h

@@ -43,6 +43,8 @@ public:
 
     static std::vector<std::string> splitStringBySpace( const std::string& s );
 
+    static int computeEditDistance( const std::string& x, const std::string& y);
+
 private:
     template <class Container>
     static void   splitByDelimiter( const std::string& str, Container& cont, char delimiter = ' ' );

ApplicationCode/UnitTests/RiaStdStringTools-Test.cpp

@@ -23,3 +23,21 @@ TEST( RiaStdStringToolsTest, ParseNumbers )
         EXPECT_TRUE( RiaStdStringTools::isNumber( text, decimalPoint ) );
     }
 }
+
+//--------------------------------------------------------------------------------------------------
+///
+//--------------------------------------------------------------------------------------------------
+TEST( RiaStdStringToolsTest, EditDistance )
+{
+    // Equal string needs zero edits
+    EXPECT_EQ( 0, RiaStdStringTools::computeEditDistance( "same", "same" ) );
+
+    // Empty strings are also zero edits
+    EXPECT_EQ( 0, RiaStdStringTools::computeEditDistance( "", "" ) );
+
+    // Examples from wikipedia
+    EXPECT_EQ( 3, RiaStdStringTools::computeEditDistance( "kitten", "sitting" ) );
+    EXPECT_EQ( 3, RiaStdStringTools::computeEditDistance( "sitting", "kitten" ) );
+    EXPECT_EQ( 3, RiaStdStringTools::computeEditDistance( "Saturday", "Sunday" ) );
+    EXPECT_EQ( 3, RiaStdStringTools::computeEditDistance( "Sunday", "Saturday" ) );
+}