We worked on Dijkstra's algorithm for CC12. You may assume the MinHeap class has been correctly implemented. Given the following complete implementation, which line contains a bug? Check the comments for LINE1, LINE 2, LINE 3

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The question asks which line contains a bug in a complete Dijkstra’s algorithm implementation with a MinHeap, and provides four answer choices. Since we do not have the actual code or the specific comments for LINE1, LINE2, and LINE3, we cannot definitively identify which line is buggy from the options alone. Here is how one would approach this kind of debugging in general, applied to Dijkstra’s algorithm with a MinHeap.

First, consider the option that claims there is no bug: 'The implementation is correct and there is NO bug.' To evaluate this, you would need to verify that every core property of Dijkstra’s algorithm is preserved throughout the run: (a) each vertex is settled exactly once with the smallest known distance, (b) all relaxations are performed properly when a vertex is popped from the MinHeap, (c) distances are updated via decrease-key or equivalent, and (d) no shorter path is overlooked due to outdated heap entries or missing decrease-key operations. If any of these invariants are violated anywhere in the code, this option becomes false. Without seeing the code, this remains a guess.

Second, examine LINE 1 for potential issues in a Dijkstra-with-MinHeap context. Common LINE1 bugs involve initialization mistakes (e.g., not initializing distances correctly, or not setting the source distance to zero), or failing to seed the priority queue with the source node. If LINE1 is responsible for starting values, an error here would cascade into incorrect relaxations later. If LINE1 is merely a comment or a harmless initialization, this may not be the bug.

Third, inspect LINE 2. In many Dijkstra implementations, a frequent bug around the heap operations is mishandling decrease-key or not removing stale entries properly. If LINE2 handles updating a vertex’s distance in the heap or enqueuing a new candidate distance, a bug here could cause the algorithm to consider a non-optimal path or fail to reflect a shorter distance when found. Another LINE2 issue could be incorrectly marking a node as visited before it’s truly settled, which would also disrupt correctness.

Fourth, assess LINE 3. This line might be involved with the relaxation step, condition checks for whether a shorter path was found, or logic that decides when a vertex is extracted from the heap. Potential problems include relaxing edges with outdated distances, performing relaxations after a node has already been finalized, or incorrect handling of adjacency iterations. A bug here could cause repeated or missed updates, breaking the algorithm’s guarantees.

Given these typical failure modes, you would compare the actual code lines to the expected behavior described above. If the code consistently preserves the invariant that the smallest-distance vertex is chosen next and all relaxations are correctly applied, the corresponding LINE would be less likely to be buggy. If you observe stale heap entries not being ignored or improper updates not being propagated, focus on the line handling the heap interactions (often LINE2) or the relaxation logic (often LINE3).

In the absence of the concrete code and the actual comments for LINE1, LINE2, and LINE3, you cannot definitively say which line contains a bug from the information given. To proceed, you would need to inspect the exact code snippets for those lines and test with a small graph to see where the algorithm diverges from expected behavior, paying close attention to: initialization, update/decrease-key operations, visited/settled flags, and the relaxation loop.

We worked on Dijkstra's algorithm for CC12. You may assume the MinHeap class has been correctly implemented. Given the following complete implementation, which line contains a bug? Check the comments for LINE1, LINE 2, LINE 3

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We worked on Dijkstra's algorithm for CC12. You may assume the MinHeap class has been correctly implemented. Given the following incomplete implementation, please choose correct code segment to complete it.

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