Milk Measurement (Silver) Debugging

Debugging Help
#1

Milk Measurement

Hi,
I have been working on this problem for a while and can’t fix test cases 6 and 9 (Wrong Answer). What’s is wrong?

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

struct Change {
    int day, cow, change;

    bool operator < (const Change& other) const {
        if (day < other.day) {
            return true;
        }

        else if (day > other.day) {
            return false;
        }

        if (cow < other.cow) {
            return true;
        }

        return cow == other.cow && change < other.change;
    }
};

int main() {
    ios_base::sync_with_stdio(false);
    cin.tie(nullptr);

    freopen("measurement.in", "r", stdin);
    freopen("measurement.out", "w", stdout);

    int length, initial;
    cin >> length >> initial;

    vector<Change> changes(length);
    unordered_map<int, int> values = {{0, initial}};
    map<int, unordered_set<int>> inverse = {{initial, unordered_set<int>{0}}};

    for (Change &change: changes) {
        cin >> change.day >> change.cow >> change.change;
        values[change.cow] = initial;
        inverse[initial].insert(change.cow);
    }

    sort(changes.begin(), changes.end());

    int highest_changes = 0;
    int leading_value = initial;

    for (Change &change: changes) {
        int value = values[change.cow] + change.change;
        unordered_set<int> &leaders = inverse[leading_value];

        if (leaders.find(change.cow) != leaders.end()) {
            if (change.change < 0) {
                auto it = inverse.rbegin();
                it--;

                if (value <= (*it).first) {
                    highest_changes++;

                    if (leaders.size() == 1) {
                        leading_value = (*it).first;
                    }
                }

                else {
                    leading_value = value;
                }
            }

            else {
                if (leaders.size() > 1) {
                    highest_changes++;
                }

                leading_value = value;
            }
        }

        else if (value >= leading_value) {
            highest_changes++;
            leading_value = value;
        }

        inverse[values[change.cow]].erase(change.cow);

        if (inverse[values[change.cow]].empty()) {
            inverse.erase(values[change.cow]);
        }

        values[change.cow] = value;
        inverse[value].insert(change.cow);
    }

    cout << highest_changes << "\n";
    return 0;
}
#2

There are some tips about debugging here: