StringEditDistance.java

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package com.sun.enterprise.admin.cli;

public class StringEditDistance {
 
     /**
      * Computes the edit distance between two strings.
      *
      * <p>
      * The complexity is O(nm) where n=a.length() and m=b.length().
      */
     public static int editDistance(String a, String b) {
         return new StringEditDistance(a, b).calc();
     }
  
     /**
      * Finds the string in the <code>group</code> closest to
      * <code>key</code> and returns it.
      *
      * @return null if group.length==0.
      */
     public static String findNearest(String key, String[] group) {
         int c = Integer.MAX_VALUE;
         String r = null;
         for (int i = 0; i < group.length; i++) {
             int ed = editDistance(key, group[i]);
             if (c > ed) {
                 c = ed;
                 r = group[i];
             }
         }
         return r;
     }
 
 
     /** cost vector. */
     private int[] cost;
 
     /** back buffer. */
     private int[] back;
 
     /** Two strings to be compared. */
     private final String a,b;
  
     private StringEditDistance(String a, String b) {
         this.a = a;
         this.b = b;
         cost = new int[a.length() + 1];
         back = new int[a.length() + 1];
         // back buffer
         for (int i = 0; i <= a.length(); i++)
             cost[i] = i;
     }
 
     /**
      * Swaps two buffers.
      */
     private void flip() {
         int[] t = cost;
         cost = back;
         back = t;
     }
  
     private int min(int a, int b, int c) {
          return Math.min(a, Math.min(b, c));
     }
 
     private int calc() {
         for (int j = 0; j < b.length(); j++) {
             flip();
             cost[0] = j + 1;
             for (int i = 0; i < a.length(); i++) {
                 int match = (a.charAt(i) == b.charAt(j)) ? 0 : 1;
                 cost[i+1] = min(back[i] + match, cost[i] + 1, back[i+1] + 1);
             }
         }
         return cost[a.length()];
     }
}