[HDOJ5734]Acperience（数学，公式推导）

题目链接：http://acm.split.hdu.edu.cn/showproblem.php?pid=5734

 1 /*
 2 ━━━━━┒ギリギリ♂ eye！
 3 ┓┏┓┏┓┃キリキリ♂ mind！
 4 ┛┗┛┗┛┃＼○／
 5 ┓┏┓┏┓┃ /
 6 ┛┗┛┗┛┃ノ)
 7 ┓┏┓┏┓┃
 8 ┛┗┛┗┛┃
 9 ┓┏┓┏┓┃
10 ┛┗┛┗┛┃
11 ┓┏┓┏┓┃
12 ┛┗┛┗┛┃
13 ┓┏┓┏┓┃
14 ┃┃┃┃┃┃
15 ┻┻┻┻┻┻
16 */
17 #include <algorithm>
18 #include <iostream>
19 #include <iomanip>
20 #include <cstring>
21 #include <climits>
22 #include <complex>
23 #include <fstream>
24 #include <cassert>
25 #include <cstdio>
26 #include <bitset>
27 #include <vector>
28 #include <deque>
29 #include <queue>
30 #include <stack>
31 #include <ctime>
32 #include <set>
33 #include <map>
34 #include <cmath>
35 using namespace std;
36 #define fr first
37 #define sc second
38 #define cl clear
39 #define BUG puts("here!!!")
40 #define W(a) while(a--)
41 #define pb(a) push_back(a)
42 #define Rint(a) scanf("%d", &a)
43 #define Rs(a) scanf("%s", a)
44 #define Cin(a) cin >> a
45 #define FRead() freopen("in", "r", stdin)
46 #define FWrite() freopen("out", "w", stdout)
47 #define Rep(i, len) for(int i = 0; i < (len); i++)
48 #define For(i, a, len) for(int i = (a); i < (len); i++)
49 #define Cls(a) memset((a), 0, sizeof(a))
50 #define Clr(a, x) memset((a), (x), sizeof(a))
51 #define Full(a) memset((a), 0x7f7f7f, sizeof(a))
52 #define lrt rt << 1
53 #define rrt rt << 1 | 1
54 #define pi 3.14159265359
55 #define RT return
56 #define lowbit(x) x & (-x)
57 #define onecnt(x) __builtin_popcount(x)
58 typedef long long LL;
59 typedef long double LD;
60 typedef unsigned long long ULL;
61 typedef pair<int, int> pii;
62 typedef pair<string, int> psi;
63 typedef pair<LL, LL> pll;
64 typedef map<string, int> msi;
65 typedef vector<int> vi;
66 typedef vector<LL> vl;
67 typedef vector<vl> vvl;
68 typedef vector<bool> vb;
69
70 const int maxn = 100100;
71 LL n;
72 LL w, w2;
73 LL K, B;
74
75 LL gcd(LL x, LL y) {
76     return y == 0 ? x : gcd(y, x%y);
77 }
78
79 int main() {
80     // FRead();
81     int T;
82     Rint(T);
83     W(T) {
84         Rint(n);
85         K = B = 0;
86         For(i, 1, n+1) {
87             cin >> w;
88             w2 = w * w;
89             B += abs(w);
90             K += w2;
91         }
92         LL p = n * K - B * B;
93         LL ex = gcd(p, n);
94         cout << p/ex << "/" << n/ex << endl;
95     }
96     RT 0;
97 }