[LightOJ1028]Trailing Zeroes (I)（拆分因子）

题目链接：http://lightoj.com/volume_showproblem.php?problem=1028
思路：求一个数的所有因子数，结果-1…数据比较大，所以要加一步优化t < prime[i] * prime[i]的时候要退出。
 1 #include <algorithm>
 2 #include <iostream>
 3 #include <iomanip>
 4 #include <cstring>
 5 #include <climits>
 6 #include <complex>
 7 #include <fstream>
 8 #include <cassert>
 9 #include <cstdio>
10 #include <bitset>
11 #include <vector>
12 #include <deque>
13 #include <queue>
14 #include <stack>
15 #include <ctime>
16 #include <set>
17 #include <map>
18 #include <cmath>
19 using namespace std;
20 #define fr first
21 #define sc second
22 #define cl clear
23 #define BUG puts("here!!!")
24 #define W(a) while(a--)
25 #define pb(a) push_back(a)
26 #define Rint(a) scanf("%d", &a)
27 #define Rll(a) scanf("%I64d", &a)
28 #define Rs(a) scanf("%s", a)
29 #define Cin(a) cin >> a
30 #define FRead() freopen("in", "r", stdin)
31 #define FWrite() freopen("out", "w", stdout)
32 #define Rep(i, len) for(int i = 0; i < (len); i++)
33 #define For(i, a, len) for(int i = (a); i < (len); i++)
34 #define Cls(a) memset((a), 0, sizeof(a))
35 #define Clr(a, x) memset((a), (x), sizeof(a))
36 #define Full(a) memset((a), 0x7f7f7f, sizeof(a))
37 #define lrt rt << 1
38 #define rrt rt << 1 | 1
39 #define pi 3.14159265359
40 #define RT return
41 #define lowbit(x) x & (-x)
42 #define onecnt(x) __builtin_popcount(x)
43 typedef long long LL;
44 typedef long double LD;
45 typedef unsigned long long ULL;
46 typedef pair<int, int> pii;
47 typedef pair<string, int> psi;
48 typedef pair<LL, LL> pll;
49 typedef map<string, int> msi;
50 typedef vector<int> vi;
51 typedef vector<LL> vl;
52 typedef vector<vl> vvl;
53 typedef vector<bool> vb;
54 
55 const int maxn = 1001000;
56 LL n;
57 LL prime[maxn], vis[maxn];
58 int pcnt;
59 
60 void init() {
61     pcnt = 0; Cls(vis);
62     for(LL i = 2; i < maxn; i++) {
63         if(!vis[i]) {
64             for(LL j = i * i; j < maxn; j+=i)
65             vis[j] = 1;
66             prime[pcnt++] = i;
67         }
68     }
69 }
70 
71 LL factor(LL x) {
72     LL ret = 1;
73     LL t = x;
74     Rep(i, pcnt) {
75         if(t < prime[i] * prime[i]) break;
76         if(t % prime[i] == 0) {
77             int k = 0;
78             while(t % prime[i] == 0) {
79                 t /= prime[i];
80                 k++;
81             }
82             ret *= (k + 1);
83         }
84     }
85     if(t > 1) ret *= 2;
86     return ret;
87 }
88 
89 int main() {
90     // FRead();
91     init();
92     int T, _ = 1;
93     Rint(T);
94     W(T) {
95         printf("Case %d: ", _++);
96         cin >> n;
97         cout << factor(n) - 1 << endl;
98     }
99 }