Google Coding Interview With A High School Student
Clément Mihailescu・2 minutes read
The video showcases a Google coding interview with competitive programmer William Lin tackling a challenging "airport connections" question, focusing on strongly connected components in a directed graph. The solution involves compressing components, adding necessary edges, and counting nodes with zero in-degree in the new graph to ensure all nodes are reachable from the starting node.
Insights
- The coding interview with William Lin focuses on solving a complex problem involving directed graphs and strongly connected components, emphasizing the compression of these components to create an acyclic graph.
- The algorithm presented in the interview involves a detailed process of identifying, compressing, and analyzing components within the graph, ultimately aiming to determine the number of nodes with an indegree of zero to ensure all nodes are reachable from the starting node.
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Recent questions
How does the Google coding interview question "airport connections" work?
The Google coding interview question "airport connections" involves determining the minimum number of one-way flights needed for passengers to travel from LaGuardia to any other airport. It is structured as a directed graph focusing on strongly connected components, where any node can reach any other node within the group. The solution includes compressing these components into new nodes to create an acyclic graph and ensuring all nodes are reachable from the starting node by adding necessary edges. The final answer is the number of nodes with an indegree of zero, excluding the starting node, in the new graph.
What steps are involved in solving the "airport connections" problem?
The solution to the "airport connections" problem includes processing input, finding strongly connected components, compressing the graph, and determining the number of nodes with an indegree of zero for the solution. This involves assigning ID numbers to airports, creating a map for each airport name to its ID, representing the graph as a Jason C-list, utilizing an adjacency list to store the graph, implementing Kosaraju's algorithm to find strongly connected components, compressing the graph based on components, and calculating the number of nodes with an in-degree of zero by counting representative nodes.
How is the time complexity of the algorithm for the "airport connections" problem evaluated?
The time complexity of the algorithm for the "airport connections" problem is determined by the number of airports and routes, with each step's complexity detailed. The complexity analysis includes binary search tree operations, loop complexities, and DFS iterations. The second DFS mirrors the first, maintaining the same time complexity, which is crucial for the algorithm's success. The reverse adjacency list creation and DFS iterations contribute to time complexity calculations.
What is the significance of compressing strongly connected components in the "airport connections" problem?
Compressing strongly connected components in the "airport connections" problem involves grouping nodes where any node can reach any other node within the group. These components are compressed into new nodes to create an acyclic graph, ensuring all nodes are reachable from the starting node by adding necessary edges. This compression simplifies the graph structure and aids in determining the minimum number of one-way flights needed for passengers to travel between airports efficiently.
How does the algorithm for the "airport connections" problem handle duplicate edges in the new adjacency list?
The algorithm for the "airport connections" problem handles duplicate edges in the new adjacency list by adding edges between representative nodes of different components. This process ensures that all necessary connections are maintained in the compressed graph, allowing for efficient traversal and calculation of the number of nodes with an in-degree of zero. By addressing duplicate edges between components, the algorithm maintains the integrity of the graph structure and accurately determines the required flights for passenger travel.