LongestCommonSubstring.java

package com.opendoorlogistics.codefromweb;

/**
 * From http://en.wikibooks.org/wiki/Algorithm_Implementation/Strings/Longest_common_substring#Java
 * @author Phil
 *
 */
public class LongestCommonSubstring {
	public static int longestSubstr(String first, String second) {
		if (first == null || second == null || first.length() == 0 || second.length() == 0) {
			return 0;
		}

		int maxLen = 0;
		int fl = first.length();
		int sl = second.length();
		int[][] table = new int[fl + 1][sl + 1];

		for (int s = 0; s <= sl; s++)
			table[0][s] = 0;
		for (int f = 0; f <= fl; f++)
			table[f][0] = 0;

		for (int i = 1; i <= fl; i++) {
			for (int j = 1; j <= sl; j++) {
				if (first.charAt(i - 1) == second.charAt(j - 1)) {
					if (i == 1 || j == 1) {
						table[i][j] = 1;
					} else {
						table[i][j] = table[i - 1][j - 1] + 1;
					}
					if (table[i][j] > maxLen) {
						maxLen = table[i][j];
					}
				}
			}
		}
		return maxLen;
	}
}