2492-minimum-score-of-a-path-between-two-cities.rb

# frozen_string_literal: true

# 2492. Minimum Score of a Path Between Two Cities
# https://leetcode.com/problems/minimum-score-of-a-path-between-two-cities

=begin

You are given a positive integer n representing n cities numbered from 1 to n. You are also given a 2D array roads where roads[i] = [ai, bi, distancei] indicates that there is a bidirectional road between cities ai and bi with a distance equal to distancei. The cities graph is not necessarily connected.

The score of a path between two cities is defined as the minimum distance of a road in this path.

Return the minimum possible score of a path between cities 1 and n.

### Note:

* A path is a sequence of roads between two cities.
* It is allowed for a path to contain the same road multiple times, and you can visit cities 1 and n multiple times along the path.
* The test cases are generated such that there is at least one path between 1 and n.

### Example 1:
Input: n = 4, roads = [[1,2,9],[2,3,6],[2,4,5],[1,4,7]]
Output: 5

### Example 2:
Input: n = 4, roads = [[1,2,2],[1,3,4],[3,4,7]]
Output: 2

### Constraints:

* 2 <= n <= 105
* 1 <= roads.length <= 105
* roads[i].length == 3
* 1 <= ai, bi <= n
* ai != bi
* 1 <= distancei <= 104
* There are no repeated edges.
* There is at least one path between 1 and n.

=end

# @param {Integer} n
# @param {Integer[][]} roads
# @return {Integer}
def min_score(n, roads)
  neighbors = Hash.new { |h, k| h[k] = [] }
  roads.each { |a, b, distance|
    neighbors[a] << [distance, b]
    neighbors[b] << [distance, a]
  }
  answer = Float::INFINITY
  queue = [1]
  visited = {}
  until queue.empty?
    node = queue.shift
    next if visited[node]
    visited[node] = true
    neighbors[node].each { |distance, neighbor|
      answer = [answer, distance].min
      queue << neighbor
    }
  end
  answer
end

# **************** #
#       TEST       #
# **************** #

require "test/unit"
class Test_min_score < Test::Unit::TestCase
  def test_
    assert_equal 5, min_score(4, [[1, 2, 9], [2, 3, 6], [2, 4, 5], [1, 4, 7]])
    assert_equal 2, min_score(4, [[1, 2, 2], [1, 3, 4], [3, 4, 7]])
  end
end