Count Ways To Build Good Strings

1class Solution {
2    public int countGoodStrings(int low, int high, int zero, int one) {
3        int dp[] = new int[high+1];
4        dp[0]=1;
5        int ans=0;
6        for(int i=1;i<=high;i++){
7            dp[i] = ((i-zero>=0 ? dp[i-zero]:0)+(i-one>=0 ? dp[i-one]:0))%1000000007;
8            if(i>=low){
9                ans = (ans+dp[i])%1000000007;
10            }
11        }
12        return ans;
13    }
14}