44 lines
889 B
C++
44 lines
889 B
C++
#include <cassert>
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#include <vector>
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class Solution {
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constexpr static int MOD = 1000000007;
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static void add_with_mod(std::vector<int>& good, std::size_t i, int value) {
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good[i] = (good[i] + value) % MOD;
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}
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public:
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int countGoodStrings(int low, int high, int zero, int one) {
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assert(low <= high);
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std::vector<int> good(high + 1, 0);
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good[0] = 1;
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for (int length = 1; length <= high; ++length) {
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if (length >= zero) {
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add_with_mod(good, length, good[length - zero]);
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}
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if (length >= one) {
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add_with_mod(good, length, good[length - one]);
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}
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}
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int total = 0;
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for (int i = low; i <= high; ++i) {
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total = (total + good[i]) % MOD;
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}
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return total;
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}
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};
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int main() {
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Solution s;
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assert(s.countGoodStrings(3, 3, 1, 1) == 8);
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assert(s.countGoodStrings(2, 3, 1, 2) == 5);
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return 0;
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}
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