可以用贪心来做，时间复杂度$O(n·logn)$

#include <iostream>
#include <cstdio>
#include <vector>
#include <cstring>
#include <algorithm>
#include <unordered_map>
#include <unordered_set>

using namespace std;

#define FAST_IO ios_base::sync_with_stdio(0); cin.tie(0); cout.tie(0);

#define MAX(a,b) ((a) > (b)? (a): (b))
#define MIN(a,b) ((a) < (b)? (a): (b))

typedef pair<int, int> pii;
typedef long long ll;

vector<pii> peo; 

int main(){
    FAST_IO;

    int T;

    cin >> T;

    while(T--){
        int n;
        cin >> n;
        peo.clear();
        for(auto i=0;i<n;i++){
            int wash, cut;
            cin >> wash >> cut;
            peo.emplace_back(wash, cut);
        }
        int sum = 0;
        int delt = 0;
        sort(peo.begin(), peo.end(), [](pii &a, pii &b){
            if(a.first <= a.second){
                if(b.first <= b.second){
                    return a.first < b.first;
                }else{
                    return true;
                }
            }else{
                if(b.first <= b.second){
                    return false;
                }else{
                    return a.second > b.second;
                }
            }
        });
        for(auto i=0;i<n;i++){
            auto item = peo[i];
            if(delt < item.first){
                sum += item.first;
                delt = item.second;
            }
            else{
                sum += item.first;
                delt -= item.first;
                delt += item.second;
            }
        }
        cout << sum + delt << endl;
    }

    return 0;
}