Count Ways To Build Good Strings

1class Solution {
2public:
3    int countGoodStrings(int low, int high, int zero, int one) {
4         int dp[high+1];
5    memset(dp, 0, sizeof(dp));
6    dp[0]=1;
7    int ans=0;
8    for(int i=1;i<=high;i++){
9        dp[i] = ((i-zero>=0 ? dp[i-zero]:0)+(i-one>=0 ? dp[i-one]:0))%1000000007;
10        if(i>=low){
11            ans = (ans+dp[i])%1000000007;
12        }
13    }
14    return ans;
15    }
16};