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Grokking the Coding Interview Patterns in C#

Solution: Reorder Routes to Make All Paths Lead to the City Zero

Explore how to solve the reorder routes problem by representing the city network as a graph and performing a depth-first search starting from city zero. Understand how to identify and reverse misoriented roads to ensure every city can reach the capital, while minimizing the number of changes. This lesson empowers you to apply graph traversal and adjacency lists effectively for solving tree-structured road networks.

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Statement

There are n cities labeled from 00 to n−1n - 1, connected by n−1n - 1 roads, so there is only one route between any two cities. This road network forms a tree structure.

Last year, the Ministry of transport made all roads one-way due to their narrow width. These roads are represented as connections, where each entry connections[i] =[ai,bi]= [a_i, b_i] means there is a road going from city aia_i to city bib_i ...