动态规划两个数组dp问题系列一＞最长公共子序列

class Solution {
    public int longestCommonSubsequence(String s1, String s2) {
        int m = s1.length(), n = s2.length();
        s1 = " "+ s1; s2 = " "+ s2;

        int[][] dp = new int[m + 1][n + 1];
        for(int i = 1; i <= m; i++)
            for(int j = 1; j <= n; j++){
                if(s1.charAt(i) == s2.charAt(j)) 
                    dp[i][j] = dp[i - 1][j - 1] + 1;
                else
                    dp[i][j] = Math.max(dp[i - 1][j], dp[i][j - 1]);
            }

        return dp[m][n];
    }
}