LongestCommonSequence 最长连续公共子序列（算法导论是最长公共子序列）

import java.util.Scanner;//最长连续公共子序列//连续i子串的特点就是如果str1[i]和str2[j]是属于某公共子串的最后一个字符，//那么一定有str1[i]==str2[j] && str1[i-1] == str2[j-1]，//从矩阵中直观的看，就是由“1”构成的“斜线”代表的序列都是公共子串，//那么最长公共子串肯定就是斜线“1”最长的那个串。public class LongestCommonSequence {/** * @param args */private int end1 = 0;private int end2 = 0;public static void main(String[] args) {// TODO Auto-generated method stubScanner scan = new Scanner(System.in);String s1 = scan.next();String s2 = scan.next();LongestCommonSequence lcs = new LongestCommonSequence();System.out.println(lcs.longestCommonSequence(s1, s2));}private String longestCommonSequence(String s1, String s2) {if (s1 == null || s1.length() == 0 || s2 == null || s2.length() == 0) {return null;}int[][] equals = new int[s1.length()][s2.length()];for (int i = 0; i < s1.length(); i++) {for (int j = 0; j < s2.length(); j++) {if (s1.charAt(i) == s2.charAt(j)) {equals[i][j] = 1;} else {equals[i][j] = 0;}}}int longestlen = getLongesPosition(equals, s1.length(), s2.length());System.out.println(longestlen + " " + end1);return s1.substring(end1 - longestlen + 1, end1 + 1);}private int getLongesPosition(int[][] equals, int len1, int len2) {int max = 0;for (int i = 0; i < len1; i++) {int flag = i;int len = 0;for (int j = 0; j < (int) Math.min(len1, len2) && flag < len1; j++) {if (equals[flag][j] == 1) {len++;} else {if (len > max) {max = len;end1 = flag - 1;end2 = j - 1;}len = 0;}flag++;}}for (int i = 1; i < len2; i++) {int flag = i;int len = 0;for (int j = 0; j < (int) Math.min(len1, len2) && flag < len2; j++) {if (equals[j][flag] == 1) {len++;} else {if (len > max) {max = len;end1 = j - 1;end2 = flag - 1;}len = 0;}flag++;}}return max;}}