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// 2466. Count Ways To Build Good Strings
#include "leetcode.h"
/*
* given the integers 'zero, one, low, and high', we can construct a string by
* starting with an empty string, and then at each step perform either of the
* following opperations:
* - append the character 0 'zero' times
* - append the character 1 'one' times
* this can be performed any number of times. a good string is a string
* constructed by the above process having a length between 'low' and 'high'
* (inclusive). return the number of different good strings that can be
* constructed. return modulo 10^9+7.
*/
class Solution {
public:
int countGoodStrings(int low, int high, int zero, int one) {
vector<int> dp(high + 1, 0);
dp[0] = 1;
int mod = 1000000007;
for (int i = 1; i <= high; ++i) {
if (i >= zero)
dp[i] += dp[i - zero] % mod;
if (i >= one)
dp[i] += dp[i - one] % mod;
}
long long cnt = 0;
for (int i = low; i <= high; ++i)
cnt = (cnt + dp[i]) % mod;
return cnt;
}
};
int main() {
Solution obj;
printf("%d\n", obj.countGoodStrings(3, 3, 1, 1)); // expect: 8
printf("%d\n", obj.countGoodStrings(2, 3, 1, 2)); // expect: 5
}
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