problems(cpp): add “2466. Count Ways To Build Good Strings”

Signed-off-by: Matej Focko <mfocko@redhat.com>

problems/count-ways-to-build-good-strings.cpp

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