题解 | 因子区间

#include <bits/stdc++.h>
using namespace std;
#define int long long
#define endl "\n"
#define inf LLONG_MAX
const int mod=1e9+7;

void solve()
{
    int n,q;
    cin>>n>>q;
    vector<int> a(n+1),cnt(1e5+1,1),s(n+1,0);
    vector<vector<int>> sum(n+1,vector<int>(129,0));
    for(int i=1;i<=n;i++)
        cin>>a[i];
    for (int i=2;i<=1e5;i++)
    {
        for (int j=i;j<=1e5;j+=i)
        {
            cnt[j]++;
        }
    }
    for (int i=1;i<=n;i++)
    {
        for (int j=0;j<=128;j++)
            sum[i][j]=sum[i-1][j];
        sum[i][cnt[a[i]]]++;
    }
    while (q--)
    {
        int l,r;
        cin>>l>>r;
        int ans=0;
        for (int i=0;i<=128;i++)
        {
            int x=sum[r][i]-sum[l-1][i];
            if (x<=1)
                continue;
            ans+=x*(x-1)/2;
        }
        cout<<ans<<endl;
    }
}

signed main(){
    ios_base::sync_with_stdio(false);
    cin.tie(nullptr);
    int t=1;
    //cin >> t;
    while(t--)
        solve();
    return 0;
}