diff --git a/1922. Count Good Numbers b/1922. Count Good Numbers new file mode 100644 index 0000000..59ee72e --- /dev/null +++ b/1922. Count Good Numbers @@ -0,0 +1,23 @@ +class Solution { +public: + int M = 1e9+7; + + long long binpow(long long a, long long b) { + a %= M; + long long res = 1; + while (b > 0) { + if (b & 1) + res = res * a % M; + a = a * a % M; + b >>= 1; + } + return res; + } + + int countGoodNumbers(long long n) { + long long even_positions = (n + 1) / 2; + long long odd_positions = n / 2; + long long result = (binpow(5, even_positions) * binpow(4, odd_positions)) % M; + return result; + } +};