题目链接
1 #include <bits/stdc++.h>
2 using namespace std;
3 typedef long long ll;
4 inline int read()
5 {
6 int x=0,f=1;char ch=getchar();
7 while(ch<'0'||ch>'9'){if(ch=='-')f=-1;ch=getchar();}
8 while(ch>='0'&&ch<='9'){x=x*10+ch-'0';ch=getchar();}
9 return x*f;
10 }
11
12 /********************************************************************/
13
14 const int maxn = 50000+5;
15 int n, m;
16 int a[maxn];
17 int sz, belong[maxn];
18 ll ans, num[maxn];
19 ll up[maxn], dw[maxn]; //分子， 分母
20
21 struct node{
22 int l, r;
23 int id;
24 }q[maxn];
25
26 ll gcd(ll x, ll y){
27 if(y == 0) return x;
28 else gcd(y, x%y);
29 }
30
31 bool cmp(node x, node y){
32 if(belong[x.l] == belong[y.l])
33 return x.r < y.r;
34 else
35 return belong[x.l] < belong[y.l];
36 }
37
38 void update(int x, int d){
39 ans -= num[a[x]]*num[a[x]];
40 num[a[x]] += d;
41 ans += num[a[x]]*num[a[x]];
42 }
43
44 int main(){
45 n = read(); m =read();
46 sz = ceil(sqrt(n*1.0));
47 for(int i = 1;i <= n;i++){
48 a[i] = read();
49 belong[i] = (i-1)/sz;
50 }
51 for(int i = 1;i <= m;i++){
52 q[i].l = read(); q[i].r = read();
53 q[i].id = i;
54 }
55 sort(q+1, q+1+m, cmp);
56 int pl = 1, pr = 0;
57 ans = 0;
58 for(int i = 1;i <= m;i++){
59 int id = q[i].id;
60 if(q[i].l == q[i].r){
61 up[id] = 0; dw[id] = 1;
62 continue;
63 }
64 if(pr < q[i].r){
65 for(int j = pr + 1;j <= q[i].r;j++){
66 update(j, 1);
67 }
68 }
69 else{
70 for(int j = pr;j > q[i].r;j--){
71 update(j, -1);
72 }
73 }
74 pr = q[i].r;
75 if(pl < q[i].l){
76 for(int j = pl;j < q[i].l;j++){
77 update(j, -1);
78 }
79 }
80 else {
81 for(int j = pl - 1;j >= q[i].l;j--){
82 update(j, 1);
83 }
84 }
85 pl = q[i].l;
86 ll aa = ans - q[i].r + q[i].l - 1;
87 ll bb = 1ll*(q[i].r - q[i].l + 1)*(q[i].r - q[i].l);
88 ll cc = gcd(aa, bb);
89 up[id] = aa/cc; dw[id] = bb/cc;
90 }
91 for(int i = 1;i <= m;i++){
92 printf("%lld/%lld\n", up[i], dw[i]);
93 }
94 return 0;
95 }
