tarjan Archives - Huahua's Tech Road https://zxi.mytechroad.com/blog/tag/tarjan/ Tue, 17 Sep 2019 04:37:32 +0000 en hourly 1 https://wordpress.org/?v=6.0.8 https://zxi.mytechroad.com/blog/wp-content/uploads/2017/09/cropped-photo-32x32.jpg tarjan Archives - Huahua's Tech Road https://zxi.mytechroad.com/blog/tag/tarjan/ 32 32 花花酱 LeetCode 1192. Critical Connections in a Network https://zxi.mytechroad.com/blog/graph/leetcode-1192-critical-connections-in-a-network/ https://zxi.mytechroad.com/blog/graph/leetcode-1192-critical-connections-in-a-network/#respond Sun, 15 Sep 2019 23:07:27 +0000 https://zxi.mytechroad.com/blog/?p=5556 There are n servers numbered from 0 to n-1 connected by undirected server-to-server connections forming a network where connections[i] = [a, b] represents a connection between servers a and b. Any server can reach any other server directly or…

The post 花花酱 LeetCode 1192. Critical Connections in a Network appeared first on Huahua's Tech Road.

]]> There are n servers numbered from 0 to n-1 connected by undirected server-to-server connections forming a network where connections[i] = [a, b] represents a connection between servers a and b. Any server can reach any other server directly or indirectly through the network.

A critical connection is a connection that, if removed, will make some server unable to reach some other server.

Return all critical connections in the network in any order.

Example 1:

Input: n = 4, connections = [[0,1],[1,2],[2,0],[1,3]]
Output: [[1,3]]
Explanation: [[3,1]] is also accepted.

Constraints:

  • 1 <= n <= 10^5
  • n-1 <= connections.length <= 10^5
  • connections[i][0] != connections[i][1]
  • There are no repeated connections.

Solution: Tarjan

Time complexity: O(v+e)
Space complexity: O(v+e)

C++

// Author: Huahua
class Solution {
public:
  vector<vector<int>> criticalConnections(int n, vector<vector<int>>& connections) {
    vector<vector<int>> g(n);
    vector<int> ts(n, INT_MAX);
    vector<vector<int>> ans;
    int t = 0;
    
    function<int(int, int)> tarjan = [&](int i, int p) {
      int min_i = ts[i] = ++t;
      for (int j : g[i]) {
        if (ts[j] == INT_MAX) {
          int min_j = tarjan(j, i);
          min_i = min(min_i, min_j);
          if (ts[i] < min_j)
            ans.push_back({i, j});
        } else if (j != p) {
          min_i = min(min_i, ts[j]);
        }
      }
      return min_i;
    };
    
    for (const auto& e : connections) {
      g[e[0]].push_back(e[1]);
      g[e[1]].push_back(e[0]);
    }
    
    tarjan(0, -1);
    return ans;
  }
};

The post 花花酱 LeetCode 1192. Critical Connections in a Network appeared first on Huahua's Tech Road.

]]> https://zxi.mytechroad.com/blog/graph/leetcode-1192-critical-connections-in-a-network/feed/ 0