{ "data": { "question": { "questionId": "1576", "questionFrontendId": "1466", "boundTopicId": null, "title": "Reorder Routes to Make All Paths Lead to the City Zero", "titleSlug": "reorder-routes-to-make-all-paths-lead-to-the-city-zero", "content": "

There are n cities numbered from 0 to n - 1 and n - 1 roads such that there is only one way to travel between two different cities (this network form a tree). Last year, The ministry of transport decided to orient the roads in one direction because they are too narrow.

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Roads are represented by connections where connections[i] = [ai, bi] represents a road from city ai to city bi.

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This year, there will be a big event in the capital (city 0), and many people want to travel to this city.

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Your task consists of reorienting some roads such that each city can visit the city 0. Return the minimum number of edges changed.

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It's guaranteed that each city can reach city 0 after reorder.

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Example 1:

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\nInput: n = 6, connections = [[0,1],[1,3],[2,3],[4,0],[4,5]]\nOutput: 3\nExplanation: Change the direction of edges show in red such that each node can reach the node 0 (capital).\n
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Example 2:

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\nInput: n = 5, connections = [[1,0],[1,2],[3,2],[3,4]]\nOutput: 2\nExplanation: Change the direction of edges show in red such that each node can reach the node 0 (capital).\n
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Example 3:

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\nInput: n = 3, connections = [[1,0],[2,0]]\nOutput: 0\n
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Constraints:

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