Today I have done leetcode's December LeetCoding Challenge with cpp.

December LeetCoding Challenge 20

Description

Keys and Rooms

There are n rooms labeled from 0 to n - 1 and all the rooms are locked except for room 0. Your goal is to visit all the rooms. However, you cannot enter a locked room without having its key.

When you visit a room, you may find a set of distinct keys in it. Each key has a number on it, denoting which room it unlocks, and you can take all of them with you to unlock the other rooms.

Given an array rooms where rooms[i] is the set of keys that you can obtain if you visited room i, return true if you can visit all the rooms, or false otherwise.

Example 1:

Input: rooms = [[1],[2],[3],[]]
Output: true
Explanation: 
We visit room 0 and pick up key 1.
We then visit room 1 and pick up key 2.
We then visit room 2 and pick up key 3.
We then visit room 3.
Since we were able to visit every room, we return true.

Example 2:

Input: rooms = [[1,3],[3,0,1],[2],[0]]
Output: false
Explanation: We can not enter room number 2 since the only key that unlocks it is in that room.

Constraints:

• n == rooms.length
• 2 <= n <= 1000
• 0 <= rooms[i].length <= 1000
• 1 <= sum(rooms[i].length) <= 3000
• 0 <= rooms[i][j] < n
• All the values of rooms[i] are unique.

Solution

class Solution {
  void dfs(vector<vector<int>>& rooms, unordered_set<int> &opened, int cur) {
    opened.insert(cur);
    for(auto key : rooms[cur]) {
      if(!opened.count(key)) {
        dfs(rooms, opened, key);
      }
    }
  }
public:
  bool canVisitAllRooms(vector<vector<int>>& rooms) {
    unordered_set<int> opened;
    dfs(rooms, opened, 0);
    return opened.size() == rooms.size();
  }
};

// Accepted
// 68/68 cases passed (19 ms)
// Your runtime beats 52.82 % of cpp submissions
// Your memory usage beats 20.02 % of cpp submissions (10.7 MB)