import java.util.*; public class Solution { /** * longest common subsequence * @param s1 string字符串 the string * @param s2 string字符串 the string * @return string字符串 */ public String LCS (String s1, String s2) { int len1 = s1.length(); int len2 = s2.length(); char[] arr1 = s1.toCharArray(); char[] arr2 = s2.toCharArray(); int[][] dp = new int[len1 + 1][len2 + 1]; // s1前i子串与s2前j子串的最长公共子序列长度 for (int i = 1; i < len1 + 1; i ++) { for (int j = 1; j < len2 + 1; j ++) { if (arr1[i-1] == arr2[j-1]) { dp[i][j] = dp[i-1][j-1] + 1; } else { dp[i][j] = Math.max(dp[i-1][j], dp[i][j-1]); } } } // 反推子序列 StringBuffer sb = new StringBuffer(); for (int i = len1, j = len2; i >= 0 && j >= 0 && sb.length() < dp[len1][len2]; i --, j --) { while (dp[i][j-1] == dp[i][j]) { j --; } while (dp[i-1][j] == dp[i][j]) { i --; } sb.insert(0, arr1[i-1]); } if (sb.length() == 0) return "-1"; return sb.toString(); } }