C++11 解题：细胞分裂问题 - 模运算优化

#include using namespace std;

const long long MOD = 998244353;

long long power(long long base, long long exponent) { long long result = 1; while (exponent > 0) { if (exponent % 2 == 1) { result = (result * base) % MOD; } base = (base * base) % MOD; exponent /= 2; } return result; }

int main() { long long a, b, k; cin >> a >> b >> k;

long long ans = (power(2, k) * a) % MOD;
if (a != b) {
    ans = (ans - power(2, k) + 1 + MOD) % MOD;
    ans = (ans * power(a - b + MOD, MOD - 2)) % MOD;
}
cout << ans << endl;

return 0;

}