计算两个中文字符串相似度——编辑距离算法
Levenshtein 距离，又称编辑距离，指的是两个字符串之间，由一个转换成另一个所需的最少编辑操作次数。
许可的编辑操作包括将一个字符替换成另一个字符，插入一个字符，删除一个字符。
编辑距离的算法是首先由俄国科学家Levenshtein提出的，故又叫Levenshtein Distance。
1、Java
public static void levenshtein(String str1, String str2) {
// 计算两个字符串的长度。
int len1 = str1.length();
int len2 = str2.length();
// 建立上面说的数组，比字符长度大一个空间
int[][] dif = new int[len1 + 1][len2 + 1];
// 赋初值，步骤B。
for (int a = 0; a <= len1; a++) {
dif[a][0] = a;
}
for (int a = 0; a <= len2; a++) {
dif[0][a] = a;
}
// 计算两个字符是否一样，计算左上的值
int temp;
for (int i = 1; i <= len1; i++) {
for (int j = 1; j <= len2; j++) {
System.out.println("i = " + i + " j = " + j + " str1 = "
+ str1.charAt(i - 1) + " str2 = " + str2.charAt(j - 1));
if (str1.charAt(i - 1) == str2.charAt(j - 1)) {
temp = 0;
} else {
temp = 1;
}
// 取三个值中最小的
dif[i][j] = min(dif[i - 1][j - 1] + temp, dif[i][j - 1] + 1,
dif[i - 1][j] + 1);
System.out.println("i = " + i + ", j = " + j + ", dif[i][j] = "
+ dif[i][j]);
}
}
System.out.println("字符串\"" + str1 + "\"与\"" + str2 + "\"的比较");
// 取数组右下角的值，同样不同位置代表不同字符串的比较
System.out.println("差异步骤：" + dif[len1][len2]);
// 计算相似度
float similarity = 1 - (float) dif[len1][len2]
/ Math.max(str1.length(), str2.length());
System.out.println("相似度：" + similarity);
}
</span></span>
2、LotusScript
Function toCompute(str1 As String ,str2 As String) As Double
Dim len1 As Integer
Dim len2 As Integer
Dim maxlen As Integer
Dim i As long
Dim j As long
Dim temp As long
Dim similarity As Double
If str1= "" Or str2 = "" Then
toCompute = 0
Else
len1 = Len(str1)
len2 = Len(str2)
Dim dif(0 To 120, 0 To 120) As Integer
If len1 > 120 Then
len1 = 120
End If
If len2 > 120 Then
len2 = 120
End If
If len1 > len2 Then
maxlen = len1
Else
maxlen = len2
End If
For i = 0 To len1 Step 1
dif(i,0) = i
Next
For i = 0 To len2 Step 1
dif(0,i) = i
Next
For i = 1 To len1 Step 1
For j = 1 To len2 Step 1
'Print "i = "& i & " j = " & j &" str1 = " & Right$(Left$(str1,i),1) &" str2 = " &Right$(Left$(str2,j),1)
If Right$(Left$(str1,i),1) = Right$(Left$(str2,j),1) Then
temp = 0
Else
temp = 1
End If
dif(i,j) = min(dif(i-1,j-1)+ temp ,dif(i,j-1)+1,dif(i-1,j)+1)
Next
Next
'Print "差异步骤： " & dif(len1 ,len2)
similarity = 1 - dif(len1 ,len2 )/maxlen
'Print "差异度：" & similarity
toCompute = similarity
'Call toLogFile("str1 = " & str1 &" str2 = " &str2 & " 相似度： " & similarity)
End If
End Function
</span></span>
优化
1、Visual Basic
Module Module1
Sub Main()
Dim str1 As String
Dim str2 As String
str1 = "今天是星期五"
str2 = "明天星期四"
Dim dis As New clsDistance(str1, str2)
Dim result As Integer
result = dis.CacuDistance()
Console.WriteLine(result)
End Sub
Public Class clsDistance
Private mCharA() As Char
Private mCharB() As Char
Private mCharALen As Integer
Private mCharBLen As Integer
Public Sub New(ByVal StrA As String, ByVal StrB As String)
mCharA = StrA.ToCharArray
mCharB = StrB.ToCharArray
mCharALen = mCharA.Length
mCharBLen = mCharB.Length
End Sub
Public Function CacuDistance() As Integer
Dim i As Integer
If mCharALen = 0 Then Return mCharBLen
If mCharBLen = 0 Then Return mCharALen
Console.WriteLine(mCharALen)
Console.WriteLine(mCharBLen)
Dim j As Integer = Min(mCharALen, mCharBLen) - 1
Dim tP1 As Integer, tP2 As Integer
tP1 = -1
tP2 = -1
For i = 0 To j
If mCharA(i) <> mCharB(i) Then
tP1 = i
Exit For
End If
Next
If tP1 = -1 Then Return Math.Abs(mCharALen - mCharBLen)
For i = 0 To j - tP1
If mCharA(mCharALen - i - 1) <> mCharB(mCharBLen - i - 1) Then
tP2 = i
Exit For
End If
Next
If tP2 = -1 Then Return Math.Abs(mCharALen - mCharBLen)
Console.WriteLine("tp1: = " & tP1)
Console.WriteLine("tp2 : = " & tP2)
Dim tA(mCharALen - tP1 - tP2) As Integer
For i = 0 To tA.GetUpperBound(0)
tA(i) = i
Next
For i = 0 To tA.GetUpperBound(0) Step 1
Console.WriteLine(" i = " + CStr(i) + " " & tA(i))
Next
Console.WriteLine("Bound: = " & tA.GetUpperBound(0))
Dim tN1 As Integer, tN2 As Integer, tN3 As Integer
For i = 0 To mCharBLen - tP1 - tP2 - 1
tN1 = tA(0)
tN2 = tN1 + 1
Console.WriteLine("i = " & i & " " & mCharB(mCharBLen - tP2 - i - 1))
For j = 1 To tA.GetUpperBound(0)
Console.WriteLine("j = " & j & " " & mCharA(mCharALen - tP2 - j))
If mCharA(mCharALen - tP2 - j) = mCharB(mCharBLen - tP2 - i - 1) Then
tN3 = tN1
Else
tN3 = Min(tA(j), tN1, tN2) + 1
End If
tA(j - 1) = tN2
tN2 = tN3
tN1 = tA(j)
Console.WriteLine("tn1 = " & tN1)
Console.WriteLine("tn2 = " & tN2)
Console.WriteLine("tn3 = " & tN3)
Next
tA(tA.GetUpperBound(0)) = tN2
Console.WriteLine(tA.GetUpperBound(0) & " " & tA(tA.GetUpperBound(0)))
Next
For i = 0 To tA.GetUpperBound(0) Step 1
Console.WriteLine(" i = " + CStr(i) + " " & tA(i))
Next
Return tA(tA.GetUpperBound(0))
End Function
Public Function Min(ByVal ParamArray Num() As Integer) As Integer
Dim tN As Integer, i As Integer
If Num.Length = 0 Then Return Nothing
tN = Num(0)
For i = 1 To Num.GetUpperBound(0)
If Num(i) < tN Then tN = Num(i)
Next
Return tN
End Function
End Class
End Module
</span>
2、Java
public static int clsDistance(String str1, String str2) {
int j;
int i;
int mCharALen, mCharBLen;
mCharALen = str1.length();
mCharBLen = str2.length();
int tp1 = -1;
int tp2 = -1;
j = Math.min(mCharALen , mCharBLen) - 1;
for (i = 0; i <= j; i++) {
if (str1.charAt(i) != str2.charAt(i)) {
tp1 = i;
break;
}
}
if (tp1 == -1) {
return Math.abs(mCharBLen - mCharALen);
}
for (i = 0; i <= j - tp1; i++) {
if (str1.charAt(mCharALen - i - 1) != str2.charAt(mCharBLen - i
- 1)) {
tp2 = i;
break;
}
}
if (tp2 == -1) {
return Math.abs(mCharALen - mCharBLen);
}
int taBound = mCharALen - tp1 - tp2;
int tA[] = new int[taBound + 1];
for (i = 0; i < tA.length; i++) {
tA[i] = i ;
}
System.out.println(Arrays.toString(tA));
int tN1, tN2, tN3;
for (i = 0; i < mCharBLen - tp1 - tp2 ; i++) {
tN1 = tA[0];
tN2 = tN1 + 1;
System.out.println("\n" + i + " " + str2.charAt(mCharBLen
- tp2 - i - 1));
for (j = 1; j < tA.length ; j++) {
System.out.print(str1.charAt(mCharALen - tp2 - j ) +" ");
if (str1.charAt(mCharALen - tp2 - j ) == str2.charAt(mCharBLen
- tp2 - i - 1)) {
tN3 = tN1;
} else {
tN3 = Math.min(tA[j], Math.min(tN1, tN2)) + 1;
}
tA[j - 1] = tN2;
tN2 = tN3;
tN1 = tA[j];
System.out.println("\ntN1 = " + tN1);
System.out.println("tN2 = " + tN2);
System.out.println("tN3 = " + tN3);
}
tA[tA.length - 1] = tN2;
System.out.println("\n"+tA[tA.length - 1] );
}
System.out.println("\n" +Arrays.toString(tA));
return tA[tA.length - 1];
}</span>
3、Lotus Script
%REM Function clsDistance Description: Comments for Function %END REM Function clsDistance(str1 As String ,str2 As String) As Double Dim mCharALen As Integer Dim mCharBLen As Integer Dim i As Integer Dim simularity As Double Dim maxlen As Integer mCharALen = Len(str1) mCharBLen = Len(str2) If mCharALen > mCharBLen Then maxlen = mCharALen Else maxlen = mCharBLen End If If str1= "" Or str2 = "" Then clsDistance = 0 Exit function End If Dim j As Integer If mCharALen > mCharBLen Then j = mCharBLen - 1 Else j = mCharALen - 1 End If Dim tP1 , tP2 As Integer tP1 = -1 tP2 = -1 For i = 0 To j Step 1 If Right$(Left$(str1,i+1),1) <> Right$(Left$(str2,i+1),1) Then tP1 = i Exit For End If Next If tP1 = -1 Then clsDistance = 1 - Abs(mCharALen - mCharBLen) / maxlen Exit Function End If For i = 0 To j - tP1 If Right$(Left$(str1,mCharALen - i),1) <> Right$(Left$(str2,mCharBLen - i),1) Then tP2 = i Exit For End If Next If tP2 = -1 Then clsDistance = 1 - Abs(mCharALen - mCharBLen) / maxlen Exit Function End If Dim tA(15000) As Integer Dim tABound As Integer tABound = mCharALen - tP1 - tP2 + 1 For i = 0 To tABound Step 1 tA(i) = i Next Dim tN1 As Integer, tN2 As Integer, tN3 As Integer For i = 0 To mCharBLen - tP1 - tP2 tN1 = tA(0) tN2 = tN1 + 1 For j = 1 To tABound If Right$(Left$(str1,mCharALen - tP2 - j + 1),1) = Right$(Left$(str2,mCharBLen - tP2 - i),1) Then tN3 = tN1 Else tN3 = Min(tA(j), tN1, tN2) + 1 End If tA(j - 1) = tN2 tN2 = tN3 tN1 = tA(j) Next tA(tABound) = tN2 Next simularity = 1 - tA(tABound) / maxlen clsDistance = simularity End Function</span>