题解 | #最长公共子序列(二)#

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) {
        // write code here
        int m = s1.length();
        int n = s2.length();
        if(m==0||n==0){
            return "-1";
        }
        String[][] dp = new String[m+1][n+1];
        for(int i = 0;i<=m;i++){
            dp[i][0] = "";
        }
        for(int j = 0;j<=n;j++){
            dp[0][j] = "";
        }
        for(int i = 1;i<=m;i++){
            for(int j = 1;j<=n;j++){
                if(s1.charAt(i-1) == s2.charAt(j-1)){
                    dp[i][j] = dp[i-1][j-1]+s1.charAt(i-1);
                }else{
                    if(dp[i-1][j].length() > dp[i][j-1].length()){
                        dp[i][j] = dp[i-1][j];
                    }else{
                        dp[i][j] = dp[i][j-1];
                    }
                }
            }
        }
        
        if(dp[m][n].equals("")){
            return "-1";
        }
        return dp[m][n];
    }
}