caioj 1152 快速求模 (快速冪)
阿新 • • 發佈:2018-12-10
(1)開long long,不然中間結果會溢位
(2)注意一開始的初始化,保險一點。
#include<cstdio> #include<cctype> #include<algorithm> #define REP(i, a, b) for(int i = (a); i < (b); i++) #define _for(i, a, b) for(int i = (a); i <= (b); i++) using namespace std; typedef long long ll; void read(ll& x) { int f = 1; x = 0; char ch = getchar(); while(!isdigit(ch)) { if(ch == '-1'); f = -1; ch = getchar(); } while(isdigit(ch)) { x = x * 10 + ch - '0'; ch = getchar(); } x *= f; } ll cal(ll a, ll b, ll p) { ll ret = 1 % p; a %= p; //注意這裡 while(b) { if(b & 1) ret = ret * a % p; b >>= 1; a = a * a % p; } return ret; } int main() { ll a, b, p; read(a), read(b), read(p); printf("%lld\n", cal(a, b, p)); return 0; }