2412. Minimum Money Required Before Transactions

You are given a 0-indexed 2D integer array transactions, where transactions[i] = [costi, cashbacki].

The array describes transactions, where each transaction must be completed exactly once in some order. At any given moment, you have a certain amount of money. In order to complete transaction i, money >= costi must hold true. After performing a transaction, money becomes money - costi + cashbacki.

Return the minimum amount of money required before any transaction so that all of the transactions can be completed regardless of the order of the transactions.

class Solution {
public:
    long long minimumMoney(vector<vector<int>>& transactions) {
        long long res = 0, over = 0;
        vector<vector<long long>> A;
        for(auto& t : transactions) {
            long long c = t[0], b = t[1];
            if(b < c) A.push_back({c,b});
            else if(c <= b) over = max(over, c);
        }
        sort(begin(A), end(A), [](auto a, auto b) {
           return a[1] == b[1] ? a[0] > b[0] : a[1] < b[1];
        });
        long long req = 0, ma = 0;
        for(auto& v : A) {
            long long c = v[0], b = v[1];
            req += c;
            res = max(res, req);
            req -= b;
            ma = max(ma, c);
        }
        return max({res, ma, req + over});
    }
};