1143.Longest Common Subsequence

class Solution {
    public int longestCommonSubsequence(String text1, String text2) {
        if(text1.isEmpty()||text2.isEmpty()){return 0;}
        int a=text1.length();
        int b=text2.length();
        int dp[][]=new int[a][b];
        for(int row[]:dp){Arrays.fill(row,-1);}
        return helper(text1,text1.length(),text2,text2.length(),dp);
    }
    static int helper(String text1,int n,String text2,int m,int[][] dp){
        if(n<0||m<0){return 0;}
       int curr[]=new int[m+1];
       int prev[]=new int[m+1];
        for(int i=1;i<=n;i++){
            for(int j=1;j<=m;j++){
                if(text1.charAt(i-1)==text2.charAt(j-1)){
                  curr[j]=1+prev[j-1];
                  }
                else{
                    int onleft=curr[j-1];
                    int onright=prev[j];
                    curr[j]=Math.max(onleft,onright);//i-1][j] 
                }
            }
            prev=Arrays.copyOf(curr,m+1);
        }
        // if(text1.charAt(a)==text2.charAt(b)){
        //     dp[a][b]= 1+helper(text1,a-1,text2,b-1,dp);
        // }
        // else{
        //       dp[a][b]= Math.max(helper(text1,a-1,text2,b,dp),helper(text1,a,text2,b-1,dp));
        // }
        return curr[m];
    }
}