1610C - Keshi Is Throwing a Party - CodeForces Solution

#include <bits/stdc++.h>
using namespace std;

#ifndef ONLINE_JUDGE
#include "debug.hpp"
#else
#define debug(...) 8
#endif

typedef long long ll;
#define f(i, x, n) for (ll i = x; i < n; i++)
#define rf(i, x, n) for (ll i = x; i >= n; i--)
#define pb push_back
#define all(x) (x).begin(), (x).end()
#define F first
#define S second
const ll p = 1e9 + 7;
const ll inf = 1e18;
const ll N = 2e5 + 5;

void solve() {
    ll n;
    cin >> n;
    vector<pair<ll,ll>> a(n);
    f(i,0,n) cin >> a[i].F >> a[i].S;
    ll l=0, r=n+1, ans=-1;
    while(l<=r) {
        ll mid = (l+r)/2;
        ll cnt=0;
        f(i,0,n) {
            if(a[i].F>=mid-cnt-1 && cnt<=a[i].S) cnt++;
        }
        if(cnt >= mid) {
            l=mid+1;
            ans=mid;
        }
        else {
            r=mid-1;
        }
    }
    cout << ans << '\n';
}

signed main()
{
    ios_base::sync_with_stdio(false);
    cin.tie(NULL);
    ll T = 1;
    cin >> T;
    while (T--)
        solve();
    return 0;
}