leetcode

0 class Solution {

1 public:

2 int countGoodStrings(int low, int high, int zero, int one) {

3 vector<int> dp(high + 1, 0);

4 dp[0] = 1;

5 int res = 0, mod = 1e9 + 7;

6 for (int i = 1; i <= high; i++) {

7 if (i >= zero) dp[i] = (dp[i] + dp[i - zero]) % mod;

8 if (i >= one) dp[i] = (dp[i] + dp[i - one]) % mod;

9 if (i >= low) res = (res + dp[i]) % mod;

10 }

11 return res;

12 }

13 };