練習一下shift==
using ll = long long;
class Solution {
public:
int countGoodNumbers(long long n) {
ll mod = 1e9 + 7;
ll cnt = 1;
bool even_end = n % 2;
ll half = n / 2, mul = 5 * 4;
while(half > 0){
if(half & 1) cnt = (cnt * mul) % mod;
mul = (mul * mul) % mod;
half >>= 1;
}
if(even_end) cnt = (cnt * 5) % mod;
return cnt;
}
};
蠻舒服的
左邊一個mul 右邊一個mul
※ 引述《sixB (6B)》之銘言：
: 1922.
: 看到這個題號就想哈秋哈秋哈秋
: 練習power加速