https://www.lydsy.com/JudgeOnline/problem.php?id=2038

题解：分块+莫队算法

参考文章：https://blog.csdn.net/weixin_43272781/article/details/86582353

/*
*@Author:   STZG
*@Language: C++
*/
#include <bits/stdc++.h>
#include<iostream>
#include<algorithm>
#include<cstdlib>
#include<cstring>
#include<cstdio>
#include<string>
#include<vector>
#include<bitset>
#include<queue>
#include<deque>
#include<stack>
#include<cmath>
#include<list>
#include<map>
#include<set>
//#define DEBUG
#define RI register int
using namespace std;
typedef long long ll;
//typedef __int128 lll;
const int N=50000+10;
const int MOD=1e9+7;
const double PI = acos(-1.0);
const double EXP = 1E-8;
const int INF = 0x3f3f3f3f;
int t,n,m,k,q;
ll ans,cnt,flag,temp,num;
int a[N];
int pos[N];
int f[N];
char str;
ll gcd(ll a,ll b){
    if(a<b)
        swap(a,b);
    while(b){
        int r=a%b;
        a=b;
        b=r;
    }
    return a;
}
struct node{
    int l,r,id;
    ll a,b;
    void mod(){
        ll tmp=gcd(a,b);
        a/=tmp;
        b/=tmp;
    }
    bool operator <(const node &S)const{
        if(pos[l]==pos[S.l])
            return pos[r]<pos[S.r];
        return pos[l]<pos[S.l];
    }

}e[N];
bool cmp(const node a,const node b){
    return a.id<b.id;
}
void modify(int p,int add){
    ans=ans+2*add*f[a[p]]+1;
    f[a[p]]+=add;
}
int main()
{
#ifdef DEBUG
	freopen("input.in", "r", stdin);
	//freopen("output.out", "w", stdout);
#endif
    scanf("%d%d",&n,&m);
    //scanf("%d",&t);
    //while(t--){}
    q=sqrt(n);
    for(int i=1;i<=n;i++)
        pos[i]=(i-1)/q+1;
    for(int i=1;i<=n;++i)
        scanf("%d",&a[i]);
    for(int i=1;i<=m;++i){
        scanf("%d%d",&e[i].l,&e[i].r);
        e[i].id=i;
    }

    sort(e+1,e+m+1);
    int l=1,r=0;
    for(int i=1;i<=m;++i){
        if(r<e[i].r){
            while(++r<e[i].r)
                modify(r,1);
            modify(r,1);
        }
        if(l>e[i].l){
            while(--l>e[i].l)
                modify(l,1);
            modify(l,1);
        }
        if(e[i].r<r){
            modify(r,-1);
            while(e[i].r<--r)
                modify(r,-1);
        }
        if(l<e[i].l){
            modify(l,-1);
            while(++l<e[i].l)
                modify(l,-1);
        }
        if(e[i].l==e[i].r){
            e[i].a=0;
            e[i].b=1;
            continue;
        }
        e[i].a=ans-(e[i].r-e[i].l+1),
        e[i].b=(ll)(e[i].r-e[i].l+1)*(e[i].r-e[i].l);
        e[i].mod();
    }
    sort(e+1,e+m+1,cmp);
    for(int i=1;i<=m;++i)
        printf("%lld/%lld\n",e[i].a,e[i].b);

    //cout << "Hello world!" << endl;
    return 0;
}