计算字符串的相似度
问题描述
分析与解法
具体代码如下：
1 package chapter3jiegouzhifa.StringSimilarity; 2 /** 3 * 计算字符串的相似度 4 * 【解法一】 5 * @author DELL 6 * 7 */ 8 public class StringSimilarity { 9 public static int CalculateStringDistance(String str1, int b1, int e1, String str2, int b2, int e2){ 10 if(b1>e1){ 11 if(b2>e2) 12 return 0; 13 else 14 return e2-b2+1; 15 } 16 if(b2>e2){ 17 if(b1>e1) 18 return 0; 19 else 20 return e1-b1+1; 21 } 22 if(str1.charAt(b1)==str2.charAt(b2)){ 23 return CalculateStringDistance(str1,b1+1,e1,str2,b2+1,e2); 24 }else{ 25 int t1 = CalculateStringDistance(str1,b1+1,e1,str2,b2,e2); 26 int t2 = CalculateStringDistance(str1,b1,e1,str2,b2+1,e2); 27 int t3 = CalculateStringDistance(str1,b1+1,e1,str2,b2+1,e2); 28 return Math.min(Math.min(t1, t2), t3)+1; 29 } 30 } 31 public static void main(String[] args) { 32 String s1 = "xabcdae"; 33 String s2 = "xfdfa"; 34 System.out.println(s1+"与"+s2+"的距离为："+CalculateStringDistance(s1,0,s1.length()-1,s2,0,s2.length()-1)); 35 36 } 37 38 }
程序运行结果如下：
xabcdae与xfdfa的距离为：5
下述代码清单3-6有误，最后的t1,t2,t3计算错误。
改进后的程序如下：
1 package chapter3jiegouzhifa.StringSimilarity; 2 /** 3 * 计算字符串的相似度 4 * 【解法二】改进算法 5 * 用空间换时间 6 * @author DELL 7 * 8 */ 9 public class StringSimilarity2 { 10 public static int CalculateStringDistance(String str1, int b1, int e1, String str2, int b2, int e2){ 11 int s[][][][] = new int[str1.length()+1][str1.length()][str2.length()+1][str2.length()]; 12 if(b1>e1){ 13 if(b2>e2) 14 return 0; 15 else 16 return e2-b2+1; 17 } 18 if(b2>e2){ 19 if(b1>e1) 20 return 0; 21 else 22 return e1-b1+1; 23 } 24 if(s[b1][e1][b2][e2]!=0) 25 return s[b1][e1][b2][e2]; 26 else{ 27 if(str1.charAt(b1)==str2.charAt(b2)){ 28 s[b1][e1][b2][e2]=CalculateStringDistance(str1,b1+1,e1,str2,b2+1,e2); 29 return s[b1][e1][b2][e2]; 30 }else{ 31 int t1,t2,t3; 32 if(s[b1+1][e1][b2][e2]!=0) 33 t1 = s[b1+1][e1][b2][e2]; 34 else{ 35 s[b1+1][e1][b2][e2] = CalculateStringDistance(str1,b1+1,e1,str2,b2,e2); 36 t1 = s[b1+1][e1][b2][e2]; 37 } 38 if(s[b1][e1][b2+1][e2]!=0) 39 t2 = s[b1][e1][b2+1][e2]; 40 else{ 41 s[b1][e1][b2+1][e2] = CalculateStringDistance(str1,b1,e1,str2,b2+1,e2); 42 t2 = s[b1][e1][b2+1][e2]; 43 } 44 if(s[b1+1][e1][b2+1][e2]!=0) 45 t3 = s[b1+1][e1][b2+1][e2]; 46 else{ 47 s[b1+1][e1][b2+1][e2] = CalculateStringDistance(str1,b1+1,e1,str2,b2+1,e2); 48 t3 = s[b1+1][e1][b2+1][e2]; 49 } 50 s[b1][e1][b2][e2] = Math.min(Math.min(t1, t2), t3)+1; 51 return s[b1][e1][b2][e2]; 52 } 53 } 54 } 55 public static void main(String[] args) { 56 String s1 = "xabcdae"; 57 String s2 = "xfdfa"; 58 System.out.println(s1+"与"+s2+"的距离为："+CalculateStringDistance(s1,0,s1.length()-1,s2,0,s2.length()-1)); 59 60 } 61 62 }
程序运行结果如下：
xabcdae与xfdfa的距离为：5