Fix: for the same k, node_cost is double counted

[codecov[bot]]

Codecov Report

All modified and coverable lines are covered by tests :white_check_mark:

Comparison is base (14894f9) 92.84% compared to head (1b44be0) 92.86%.

Additional details and impacted files

```diff @@ Coverage Diff @@ ## main #89 +/- ## ========================================== + Coverage 92.84% 92.86% +0.01% ========================================== Files 20 20 Lines 7617 7621 +4 ========================================== + Hits 7072 7077 +5 + Misses 545 544 -1 ```

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