Friend_and_the_Restaurant.cpp

#include<bits/stdc++.h>
#include <ext/pb_ds/assoc_container.hpp>
#include <ext/pb_ds/tree_policy.hpp>
using namespace __gnu_pbds;
using namespace std;
#define ordered_set tree<ll, null_type,less<ll>, rb_tree_tag,tree_order_statistics_node_update>
#define ll long long
#define ff first
#define ss second
#define pb push_back
#define mp make_pair
#define mii map<ll,ll>
#define pii pair<ll,ll>
#define vi vector<ll>
const ll MOD = 1e9+7;
#define REP(i,a,b) for(ll i=a;i<b;i++)
#define input vi arr;REP(i,0,n){ll ele;cin>>ele;arr.pb(ele);}
bool cmps(pii a,pii b)
{
    return a.ss<b.ss;
}
void  solve()
{
    int n;
    cin>>n;
    vi x,y;
    REP(i,0,n)
    {
        int ele;
        cin>>ele;
        x.pb(ele);
    }   
    REP(i,0,n)
    {
        int ele;
        cin>>ele;
        y.pb(ele);
    }

    multiset<ll> arr;
    REP(i,0,n)
    {
        arr.insert(y[i]-x[i]);
    }
    ll count=0;
    auto it=arr.begin();
    ll size=n;
    while(it!=arr.end())
    {
        auto add=arr.lower_bound(abs(*it));
        if(*it<0)
        {
            if(add!=arr.end())
            {
                arr.erase(add);
                count++;
                size-=2;
                it++;
                continue;
            }
            it++;
            size--;
        }
        else
        {
            count+=(size)/2;
            break;
        }
    }
    cout<<count;
    return ;
}
int main()
{
    ll t;
    cin>>t;
    while(t--)
    {
        solve();
        cout<<"\n";
    }
    return 0;
}