使用字符串DP | #最长公共子序列(二)#

public class Solution {

    public String LCS (String s1, String s2) {
        int n1 = s1.length(), n2 = s2.length();
        String[][] dp = new String[n1 + 1][n2 + 1];
        for (int i = 0; i <= n1; i++) {
            Arrays.fill(dp[i], "");
        }
        for (int i = 1; i <= n1; i++) {
            for (int j = 1; j <= n2; j++) {
                int maxDpI = i, maxDPj = j - 1;
                if (dp[i - 1][j].length() > dp[i][j - 1].length()) {
                    maxDpI = i-1;
                    maxDPj = j;
                }
                if (s1.charAt(i - 1) == s2.charAt(j - 1)) {
                    dp[i][j] = dp[i - 1][j - 1] + s1.charAt(i - 1);
                } else {
                    dp[i][j] = dp[maxDpI][maxDPj];
                }
            }
        }
        return dp[n1][n2].equals("") ? "-1" : dp[n1][n2];
    }
}