HDU 1405

题意:

　　输入一个数n，输出它的素因子与这个素因子出现的次数.

分析:

　　用欧拉函数，变下形就好了，不再过多解释.

代码如下：

 1 #include <iostream>
 2 #include <cstdio>
 3 #include <cstring>
 4 #include <fstream>
 5 #include <ctime>
 6 #include <cmath>
 7 #include <cstdlib>
 8 #include <algorithm>
 9 #include <set>
10 #include <map>
11 #include <list>
12 #include <stack>
13 #include <queue>
14 #include <iterator>
15 #include <vector>
16
17 using namespace std;
18
19 #define LL long long
20 #define INF 0x3f3f3f3f
21 #define MOD 1000000007
22 #define MAXN 10000010
23 #define MAXM 1000010
24
25 const int maxn = 65537;
26 int a[maxn];
27
28 void euler_phi(int n)
29 {
30     int m = (int)sqrt(n+0.5);
31     //int ans = n;
32     for(int i = 2; i <= m; i++ )
33         if(n%i==0)
34         {
35             //ans = ans/i*(i-1);
36             while(n%i==0)
37             {
38                 a[i]++;
39                 n /= i;
40             }
41         }
42     if(n > 1)
43         a[n]++;
44 //        ans = ans/n*(n-1);
45 //    return ans;
46 }
47
48 int main()
49 {
50     int n;
51     int kase = 0;
52     while(scanf("%d", &n)==1&&n>=0)
53     {
54         if(kase)
55             printf("\n");
56         memset(a, 0, sizeof(a));
57         euler_phi(n);
58         printf("Case %d.\n", ++kase);
59         for(int i = 2; i <= n; i++ )
60             if(a[i])
61                 printf("%d %d ", i, a[i]);
62         printf("\n");
63     }
64
65     return 0;
66 }