UVA 10892 LCM Cardinality

Posted 2020-09-09 莫兹ACM

题目链接：UVA-10892

题意为给定一个数n，问有多少组不同的数对<a,b>的lcm等于n。看了AC，∑ndless的题解，直接摘抄了。

 

代码：

 1 #include"cstdio"
 2 #include"iostream"
 3 #include"cstring"
 4 #include"algorithm"
 5 #include"cstdlib"
 6 #include"vector"
 7 #include"set"
 8 using namespace std;
 9 typedef long long LL;
10 const LL MAXN=1e5;
11 
12 LL prime[MAXN+1];
13 void getPrime()
14 {
15     memset(prime,0,sizeof(prime));
16     for(LL i=2;i<=MAXN;i++)
17     {
18         if(!prime[i])prime[++prime[0]]=i;
19         for(LL j=1;j<=prime[0]&&prime[j]<=MAXN/i;j++)
20         {
21             prime[prime[j]*i]=1;
22             if(i%prime[j]==0) break;
23         }
24     }
25 }
26 
27 int main()
28 {
29 #ifdef LOCAL
30     freopen("in.txt","r",stdin);
31     //freopen("out.txt","w",stdout);
32 #endif
33     getPrime();
34     LL n;
35     LL nn;
36     while(scanf("%lld",&n)!=EOF && n)
37     {
38         LL ans=1;
39         nn=n;
40         for(LL i=1;i<=prime[0];i++)
41         {
42             LL r=0;
43             while(n%prime[i]==0)
44             {
45                 r++;
46                 n/=prime[i];
47             }
48             ans*=(2*r+1);
49             if(n==1) break;
50         }
51         if(n>1) ans*=3;
52         ans = (ans+1)/2;
53         printf("%lld %lld\\n",nn,ans);
54     }
55     return 0;
56 }