Damerau–Levenshtein Distance的java实现

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简单实现

public class DamerauLevenshteinDistance {
	private int getDistance(String s1,String s2){
		int m= (s1==null)?0:s1.length();
		int n= (s2==null)?0:s2.length();
		if(m==0){
			return n;
		}
		if(n==0){
			return m;
		}
		int[][] d=new int[m+1][n+1];
		
		
		for(int i=0;i<=m;i++){
			d[i][0]=i;
		}
		for(int i=1;i<=n;i++){
			d[0][i]=i;
		}
		char s1_c,s2_c;
		int cost=0;
		for(int i=1;i<=m;i++){
			s1_c=s1.charAt(i-1);
			for(int j=1;j<=n;j++){
				s2_c=s2.charAt(j-1);
				cost=(s1_c==s2_c)?0:1;
				d[i][j]=Math.min(Math.min(d[i-1][j],d[i][j-1])+1,d[i-1][j-1]+cost);
				if(i>=2&&j>=2&&s1_c==s2.charAt(j-2)&&s1.charAt(i-2)==s2_c){
					d[i][j]=Math.min(d[i][j], d[i-2][j-2]+cost);
				}
			}
		}
		return d[m][n];
	}
	
	public float getSimilarity(String s1,String s2){
		if(s1==null||s2==null){
			if(s1==s2){
				return 1.0f;
			}
			return 0.0f;
		}
		float d=getDistance(s1,s2);
		return 1-(d/Math.max(s1.length(), s2.length()));
	}
}

优化后

public class DamerauLevenshteinDistance2 {
	private int getDistance(String s1,String s2){
		int m= (s1==null)?0:s1.length();
		int n= (s2==null)?0:s2.length();
		if(m==0){
			return n;
		}
		if(n==0){
			return m;
		}
		int[] p=new int[n+1];
		int[] p1=new int[n+1];
		int[] t=new int[n+1];
		for(int i=0;i<p.length;i++){
			p[i]=i;
		}
		int d=0;
		int cost=0;
		char s1_c,s2_c;
		for(int i=0;i<m;i++){
			t[0]=i+1;
			s1_c=s1.charAt(i);
			for(int j=1;j<p.length;j++){
				s2_c=s2.charAt(j-1);
				cost=(s1_c==s2_c)?0:1;
				d=Math.min(Math.min(t[j-1],p[j])+1,p[j-1]+cost);
				if(i>0&&j>1&&s1_c==s2.charAt(j-2)&&s1.charAt(i-1)==s2_c){
						d=Math.min(d,p1[j-2]+cost);
				}
				t[j]=d;
			}
			p1=p;
			p=t;
			t=new int[n+1];
		}
		return d;
	}
	
	public float getSimilarity(String s1,String s2){
		if(s1==null||s2==null){
			if(s1==s2){
				return 1.0f;
			}
			return 0.0f;
		}
		float d=getDistance(s1,s2);
		return 1-(d/Math.max(s1.length(), s2.length()));
	}
}

简单测试

import org.junit.Test;

public class DamerauLevenshteinDistanceTest {

	@Test
	public void testGetSimilarity() {
		String s1="aborad";
		String s2="aboard";
		DamerauLevenshteinDistance dld=new DamerauLevenshteinDistance();
		System.out.println(dld.getSimilarity(s1, s2));
		DamerauLevenshteinDistance2 dld2=new DamerauLevenshteinDistance2();
		System.out.println(dld2.getSimilarity(s1, s2));
	}
}