Spot Capacity Round Trips tests accept the two largest rising runs

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Seit 13.11.2026.

  • #692 von @peter1001136 — offen

Bewertung

Schwierigkeit
2/5
Geschätzter Aufwand
1-3 Stunden
Anfängerfreundlichkeit
78/100
Issue-Typ
Bug
Klarheit
Klar beschrieben
Aktivitätsstatus
Aktiv
Tech-Stack
cpp, json
Bereich
testing, tooling

Rechercherichtung

Beginne mit problem-bank/judges.json und suche die Fälle zu Spot Capacity Round Trips. Füge die gemeldete Eingabe [[1,2,4,2,5,7,2,4,9,0]] mit dem erwarteten Wert 13 hinzu und generiere anschließend die Judges wie angefordert neu. Erledigt ist die Aufgabe, wenn der hinzugefügte Fall die beschriebene falsche Lösung zurückweist, während eine korrekte Lösung weiterhin besteht.

Vom Indexierungsmodell aus dem Issue-Text verfasst.

Beschreibung

Observed behavior

In Spot Capacity Round Trips (best-time-to-buy-and-sell-stock-iii, LeetCode 123), the built-in tests accept a solution that splits the prices into rising runs and adds the two largest run gains. It passes 6/6, the same as a correct solution.

class Solution {
public:
    int bestTwoRoundTrips(vector<int>& prices) {
        vector<int> gains;
        int n = prices.size(), i = 0;
        while (i < n - 1) {
            int j = i;
            while (j + 1 < n && prices[j + 1] >= prices[j]) j++;
            if (prices[j] > prices[i]) gains.push_back(prices[j] - prices[i]);
            i = j > i ? j + 1 : i + 1;
        }
        sort(gains.rbegin(), gains.rend());
        int total = 0;
        for (int k = 0; k < (int)gains.size() && k < 2; k++) total += gains[k];
        return total;
    }
};

It never joins two runs into one trade across a dip. On [1,2,4,2,5,7,2,4,9,0] the runs gain 3, 5 and 7, so it returns 12. The answer is 13: buy at 1 and sell at 7, then buy at 2 and sell at 9. Every built-in case has at most two rising runs, or its best pair of trades is already two whole runs, so the tests cannot tell the two apart. The same solution written in Python also passes all 6 and returns 12 on the case above, since every language runs the same judge cases.

Expected behavior

At least one built-in case has three or more rising runs where the best two trades span a dip, so this solution fails the tests. A correct solution still passes every case.

Reproduction
  1. Run CodeTrial at the revision below and open Spot Capacity Round Trips with C++.
  2. Paste the solution above and run the tests. All 6 built-in cases pass.
  3. Under "Add a case", enter [[1,2,4,2,5,7,2,4,9,0]] as the input and 13 as the expected value, then run again. The new case fails with got 12.
CodeTrial version

codetrial 0.1.0 (c54aed7), built from source. The judge for this problem is unchanged between c54aed7 and main at d0544857.

Environment
  • OS: Windows 11 with the server in WSL2
  • Browser: Chrome 157.0.8103.51
  • Language: C++
  • Interview loop: Coding
  • Problem: Spot Capacity Round Trips (LeetCode 123)
  • REACTO or STAR step: Test
  • Reconnect: None
Sanitized evidence

All 6 built-in cases pass, and the added case fails with got 12:

image
Public data confirmation
  • I removed credentials, session tokens, candidate recordings, and personal interview content from this public report.

I would like to fix this by adding that case to problem-bank/judges.json and regenerating the judges. Please assign it to me.

Vorherrschende Sprache
Rust
Sterne
228
Forks
150
Ø Merge
1 T. 3 Std.
Gemergte PRs (30 T.)
226

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