Why does greedy not work here?

I'm trying to solve https://leetcode.com/problems/maximum-subsequence-score My algorithm greedily chooses the best choice until we reach k But some large 1000 number test case is failing. I'm not able to understand. AI couldn't help me come up with a smaller case that fails class Solution { public: long long maxScore(vector& nums1, vector& nums2, int k) { unordered_set selectedIndices = {}; long long selectedSum = 0; long long selectedProd = LONG_MAX; for (long long i = 0; i < k; i++) { long long newSum = 0; long long newProd = LONG_MIN; long long newIndex = 0; long long currentMaxProd = LONG_MIN; for (long long j = 0; j < nums2.size(); j++) { if (selectedIndices.find(j) != selectedIndices.end()) { continue; } long long updatedProd = (selectedSum + (long long) nums1[j]) * min(selectedProd, (long long) nums2[j]); if(updatedProd > currentMaxProd) { currentMaxProd = updatedProd; newIndex = j; newSum = nums1[j]; newProd = min(selectedProd, (long long) nums2[j]); } } selectedSum += newSum; selectedProd = newProd; cout

May 6, 2025 - 09:59

I'm trying to solve https://leetcode.com/problems/maximum-subsequence-score

My algorithm greedily chooses the best choice until we reach k

But some large 1000 number test case is failing. I'm not able to understand. AI couldn't help me come up with a smaller case that fails

class Solution {
public:
    long long maxScore(vector& nums1, vector& nums2, int k) {

        unordered_set selectedIndices = {};
        long long selectedSum = 0;
        long long selectedProd = LONG_MAX;

        for (long long i = 0; i < k; i++) {
            long long newSum = 0;
            long long newProd = LONG_MIN;
            long long newIndex = 0;
            long long currentMaxProd = LONG_MIN;
            for (long long j = 0; j < nums2.size(); j++) {
                if (selectedIndices.find(j) != selectedIndices.end()) {
                    continue;
                }

                long long updatedProd = (selectedSum + (long long) nums1[j]) * min(selectedProd, (long long) nums2[j]);
                if(updatedProd > currentMaxProd) {
                    currentMaxProd = updatedProd;
                    newIndex = j;
                    newSum = nums1[j];
                    newProd = min(selectedProd, (long long) nums2[j]);
                }
            }
             
            selectedSum += newSum;
            selectedProd = newProd;
            cout << " Selecting " << newSum << " " << selectedProd << endl;
            selectedIndices.insert(newIndex);
        }

        cout << "count: " << selectedIndices.size() << "  " << selectedSum << " " << selectedProd << endl; 

        return selectedSum * selectedProd;
        
    }
};