com.lyncode.pal.utils.StringUtils Maven / Gradle / Ivy
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package com.lyncode.pal.utils;
public class StringUtils {
public static String longestSubstring(String str1, String str2) {
StringBuilder sb = new StringBuilder();
if (str1 == null || str1.isEmpty() || str2 == null || str2.isEmpty())
return "";
// ignore case
str1 = str1.toLowerCase();
str2 = str2.toLowerCase();
// java initializes them already with 0
int[][] num = new int[str1.length()][str2.length()];
int maxlen = 0;
int lastSubsBegin = 0;
for (int i = 0; i < str1.length(); i++) {
for (int j = 0; j < str2.length(); j++) {
if (str1.charAt(i) == str2.charAt(j)) {
if ((i == 0) || (j == 0))
num[i][j] = 1;
else
num[i][j] = 1 + num[i - 1][j - 1];
if (num[i][j] > maxlen) {
maxlen = num[i][j];
// generate substring from str1 => i
int thisSubsBegin = i - num[i][j] + 1;
if (lastSubsBegin == thisSubsBegin) {
//if the current LCS is the same as the last time this block ran
sb.append(str1.charAt(i));
} else {
//this block resets the string builder if a different LCS is found
lastSubsBegin = thisSubsBegin;
sb = new StringBuilder();
sb.append(str1.substring(lastSubsBegin, i + 1));
}
}
}
}}
return sb.toString();
}
}