高精度、大整数幂取模

/*
* FZU1759.cpp
*
*  Created on: 2011-10-11
*      Author: bjfuwangzhu
*/
#include<stdio.h>
#include<string.h>
#include<math.h>
#include<stdlib.h>
#define LL long long
#define nnum 1000005
#define nmax 31625
int flag[nmax], prime[nmax];
int plen;
void mkprime() {
int i, j;
memset(flag, -1, sizeof(flag));
for (i = 2, plen = 0; i < nmax; i++) {
if (flag[i]) {
prime[plen++] = i;
}
for (j = 0; (j < plen) && (i * prime[j] < nmax); j++) {
flag[i * prime[j]] = 0;
if (i % prime[j] == 0) {
break;
}
}
}
}
int getPhi(int n) {
int i, te, phi;
te = (int) sqrt(n * 1.0);
for (i = 0, phi = n; (i < plen) && (prime[i] <= te); i++) {
if (n % prime[i] == 0) {
phi = phi / prime[i] * (prime[i] - 1);
while (n % prime[i] == 0) {
n /= prime[i];
}
}
}
if (n > 1) {
phi = phi / n * (n - 1);
}
return phi;
}
int cmpBigNum(int p, char *ch) {
int i, len;
LL res;
len = strlen(ch);
for (i = 0, res = 0; i < len; i++) {
res = (res * 10 + (ch[i] - '0'));
if (res > p) {
return 1;
}
}
return 0;
}
int getModBigNum(int p, char *ch) {
int i, len;
LL res;
len = strlen(ch);
for (i = 0, res = 0; i < len; i++) {
res = (res * 10 + (ch[i] - '0')) % p;
}
return (int) res;
}
int modular_exp(int a, int b, int c) {
LL res, temp;
res = 1 % c, temp = a % c;
while (b) {
if (b & 1) {
res = res * temp % c;
}
temp = temp * temp % c;
b >>= 1;
}
return (int) res;
}
void solve(int a, int c, char *ch) {
int phi, res, b;
phi = getPhi(c);
if (cmpBigNum(phi, ch)) {
b = getModBigNum(phi, ch) + phi;
} else {
b = atoi(ch);
}
res = modular_exp(a, b, c);
printf("%d\n", res);
}
int main() {
#ifndef ONLINE_JUDGE
freopen("data.in", "r", stdin);
#endif
int a, c;
char cha[nnum], chb[nnum];
mkprime();
while (~scanf("%s %s %d", cha, chb, &c)) {
a = getModBigNum(c, cha);
solve(a, c, chb);
}
return 0;
}