Apache
/
commons-lang
mirror of https://github.com/apache/commons-lang.git
1
0
Fork 0
Code Issues Packages Projects Releases Wiki Activity

LANG-1277: StringUtils#getLevenshteinDistance reduce memory consumption 

minimal clean-up

add changes.xml entry
This commit is contained in:
pascalschumacher 2016-10-20 21:51:01 +02:00
parent 103b64a373
commit 6423a76655
2 changed files with 9 additions and 15 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

1
src/changes/changes.xml
View File

@ -46,6 +46,7 @@ The <action> type attribute can be add,update,fix,remove.
<body>
<release version="3.6" date="tba" description="tba">
<action issue="LANG-1277" type="update" dev="pschumacher" due-to="yufcuy">StringUtils#getLevenshteinDistance reduce memory consumption</action>
<action issue="LANG-1070" type="fix" dev="pschumacher" due-to="Paul Pogonyshev">ArrayUtils#add confusing example in javadoc</action>
<action issue="LANG-1271" type="fix" dev="pschumacher" due-to="Pierre Templier">StringUtils#isAnyEmpty and #isAnyBlank should return false for an empty array</action>
<action issue="LANG-1270" type="add" dev="pschumacher" due-to="Pierre Templier">Add StringUtils#isAnyNotEmpty and #isAnyNotBlank</action>

23
src/main/java/org/apache/commons/lang3/StringUtils.java
View File

@ -7736,11 +7736,9 @@ public class StringUtils {
* another, where each change is a single character modification (deletion,
* insertion or substitution).</p>
*
* <p>The previous implementation of the Levenshtein distance algorithm
* was from <a href="https://web.archive.org/web/20120526085419/http://www.merriampark.com/ldjava.htm">
* https://web.archive.org/web/20120526085419/http://www.merriampark.com/ldjava.htm</a></p>
*
* <p>This implementation only need one single-dimensional arrays of length s.length() + 1</p>
* <p>The implementation uses a single-dimensional array of length s.length() + 1. See
* <a href="http://blog.softwx.net/2014/12/optimizing-levenshtein-algorithm-in-c.html">
* http://blog.softwx.net/2014/12/optimizing-levenshtein-algorithm-in-c.html</a> for details.</p>
*
* <pre>
* StringUtils.getLevenshteinDistance(null, *) = IllegalArgumentException
@ -7768,13 +7766,8 @@ public class StringUtils {
throw new IllegalArgumentException("Strings must not be null");
}
/*
This implementation use two variable to record the previous cost counts,
So this implementation use less memory than previous impl.
*/
int n = s.length(); // length of s
int m = t.length(); // length of t
int n = s.length();
int m = t.length();
if (n == 0) {
return m;
@ -7799,19 +7792,19 @@ public class StringUtils {
int upper;
char t_j; // jth character of t
int cost; // cost
int cost;
for (i = 0; i <= n; i++) {
p[i] = i;
}
for (j = 1; j <= m; j++) {
upper_left = p[0];
upper_left = p[0];
t_j = t.charAt(j - 1);
p[0] = j;
for (i = 1; i <= n; i++) {
upper = p[i];
upper = p[i];
cost = s.charAt(i - 1) == t_j ? 0 : 1;
// minimum of cell to the left+1, to the top+1, diagonally left and up +cost
p[i] = Math.min(Math.min(p[i - 1] + 1, p[i] + 1), upper_left + cost);