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3528. Unit Conversion I

  • Time: $O(n)$
  • Space: $O(n)$
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class Solution {
 public:
  vector<int> baseUnitConversions(vector<vector<int>>& conversions) {
    constexpr int kMod = 1'000'000'007;
    const int n = conversions.size() + 1;
    vector<int> ans(n);
    ans[0] = 1;
    queue<int> q{{0}};
    vector<vector<pair<int, int>>> graph(n);

    for (const vector<int>& conversion : conversions) {
      const int u = conversion[0];
      const int v = conversion[1];
      const int factor = conversion[2];
      graph[u].emplace_back(v, factor);
    }

    while (!q.empty()) {
      const int u = q.front();
      q.pop();
      for (const auto& [v, factor] : graph[u]) {
        ans[v] = (static_cast<long>(ans[u]) * factor) % kMod;
        q.push(v);
      }
    }

    return ans;
  }
};

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class Solution {
  public int[] baseUnitConversions(int[][] conversions) {
    final int MOD = 1_000_000_007;
    final int n = conversions.length + 1;
    int[] ans = new int[n];
    ans[0] = 1;
    Queue<Integer> q = new ArrayDeque<>(Arrays.asList(0));
    List<Pair<Integer, Integer>>[] graph = new List[n];

    for (int i = 0; i < n; i++)
      graph[i] = new ArrayList<>();

    for (int[] conversion : conversions) {
      final int u = conversion[0];
      final int v = conversion[1];
      final int factor = conversion[2];
      graph[u].add(new Pair<>(v, factor));
    }

    while (!q.isEmpty()) {
      final int u = q.poll();
      for (Pair<Integer, Integer> pair : graph[u]) {
        final int v = pair.getKey();
        final int factor = pair.getValue();
        ans[v] = (int) ((long) ans[u] * factor % MOD);
        q.offer(v);
      }
    }

    return ans;
  }
}

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class Solution:
  def baseUnitConversions(self, conversions: list[list[int]]) -> list[int]:
    MOD = 1_000_000_007
    n = len(conversions) + 1
    ans = [0] * n
    ans[0] = 1
    q = collections.deque([0])
    graph = [[] for _ in range(n)]

    for u, v, factor in conversions:
      graph[u].append((v, factor))

    while q:
      u = q.popleft()
      for v, factor in graph[u]:
        ans[v] = (ans[u] * factor) % MOD
        q.append(v)

    return ans