Aladdin and the Flying Carpet LightOJ - 1341（算数基本定理）

题目链接：qaq

题意：找出符合的因子对数的个数

思路：知道算数基本定理后就简单了（感觉和暴力的复杂度一样啊QAQ。。难受）

附上代码：

[code]#include<cstdio>
#include<cmath>
#include<cstring>
#include<cstdlib>
#include<algorithm>
using namespace std;
const int MAXN = 1000100;
int prime[MAXN + 1];
long long sum=1;
void getPrime() {
memset(prime, 0, sizeof(prime));
for (int i = 2; i <= MAXN; i++) {
if (!prime[i])prime[++prime[0]] = i;
for (int j = 1; j <= prime[0] && prime[j] <= MAXN / i; j++) {
prime[prime[j] * i] = 1;
if (i%prime[j] == 0) break;
}
}
}
long long factor[100][2];
int fatCnt;
void getFactors(long long x) {
fatCnt = 0;
long long tot=0;
long long tmp = x;
for (int i = 1; prime[i] <= tmp / prime[i]; i++) {
factor[fatCnt][1] = 0;
tot=0;
if (tmp%prime[i] == 0) {
factor[fatCnt][0] = prime[i];
while (tmp%prime[i] == 0) {
factor[fatCnt][1]++;
tmp /= prime[i];
tot++;
}
sum*=(tot+1);
fatCnt++;
}
}
if (tmp != 1) {
factor[fatCnt][0] = tmp;
factor[fatCnt++][1] = 1;
sum*=2;
}
}
int main (void){
int t;
scanf("%d",&t);
int ca=1;
getPrime();
while(t--){
sum=1;
long long n,m;
scanf("%lld%lld",&n,&m);
printf("Case %d: ",ca++);
if(m>sqrt(n)){
printf("0\n");
continue;
}
getFactors(n);
//printf("%d\n",sum);
sum=sum/2;
for(int i=1;i<m;i++){
if(n%i==0) sum--;
}
printf("%lld\n",sum);
}
return 0;
}