Find Longest Common Subsequence Length of two strings

Problem:
Given two strings: "AGGTAB", "GXTXAYB", find the length of the longest common subsequence.

The answer for the two strings is 4, "GTAB". Note subsequence is the substring of string with the characters appears in the order as they are in the string but not necessary contiguously.

Solution 1. 

Do it recursively

 /* do it recursively

* @param s1

* @param s2

* @return

*/

public static int findLongestCommonSubsequence(String s1, String s2){

if(s1.isEmpty() || s2.isEmpty())

return 0;

String substring1 = s1.substring(0, s1.length()-1);

String substring2 = s2.substring(0, s2.length()-1);

if(s1.charAt(s1.length()-1) == s2.charAt(s2.length()-1)) {

return 1+StringQ.findLongestCommonSubsequence(substring1, substring2);

} else{

return Math.max(StringQ.findLongestCommonSubsequence(s1, substring2), StringQ.findLongestCommonSubsequence(substring1, s2));

}

} 

Solution 2.

Do it iteratively:

       public static int findLongestCommonSubsequence2(String s1, String s2){

char[] cArray1 = s1.toCharArray();

char[] cArray2 = s2.toCharArray();

int[][] lcs = new int[s1.length()+1][s2.length()+1];

for(int i=0; i<cArray1.length; i++){

for(int j=0; j<cArray2.length; j++){

if(cArray1[i] == cArray2[j])

lcs[i+1][j+1] = lcs[i][j] + 1;

else

lcs[i+1][j+1] = Math.max(lcs[i+1][j], lcs[i][j+1]);

}

}

return lcs[s1.length()][s2.length()];

}