Count ways to N'th Stair(Order does not matter) .txt

class DynamicProgramming{
    
    // function to find number of ways 
    Long countWays(int m){
        int[] arr={1,2};
        long[][] dp=new long[m+1][arr.length];
        for(int i=0;i<m+1;i++)
        {
            for(int j=0;j<arr.length;j++)
            {
                dp[i][j]=-1;
            }
        }
        return countways(m,arr,0,dp);
        
    }
    Long countways(int m,int[] arr,int i,long[][] dp)
    {
        if(m==0)
        {
            return 1l;
        }
        if(arr.length==i)
        {
            return 0l;
        }
        if(dp[m][i]!=-1)
        {
            return dp[m][i];
        }
        long smallans1=0;
        if(m-arr[i]>=0)
        {
            smallans1=countways(m-arr[i],arr,i,dp);
        }
        long smallans2=countways(m,arr,i+1,dp);
        dp[m][i]=smallans1+smallans2;
        return dp[m][i];
    }
}