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

June LeetCoding Challenge 4

Description

Number of Provinces

There are n cities. Some of them are connected, while some are not. If city a is connected directly with city b, and city b is connected directly with city c, then city a is connected indirectly with city c.

A province is a group of directly or indirectly connected cities and no other cities outside of the group.

You are given an n x n matrix isConnected where isConnected[i][j] = 1 if the ith city and the jth city are directly connected, and isConnected[i][j] = 0 otherwise.

Return the total number of provinces.

Example 1:

Input: isConnected = [[1,1,0],[1,1,0],[0,0,1]]
Output: 2

Example 2:

Input: isConnected = [[1,0,0],[0,1,0],[0,0,1]]
Output: 3

Constraints:

• 1 <= n <= 200
• n == isConnected.length
• n == isConnected[i].length
• isConnected[i][j] is 1 or 0.
• isConnected[i][i] == 1
• isConnected[i][j] == isConnected[j][i]

Solution

struct UnionSet {
  vector<int> parent;
public:
  UnionSet(int size): parent(size) {
    for(int i = 0; i < size; ++i) {
      parent[i] = i;
    }
  }

  int find(int x) {
    if(parent[x] != x) parent[x] = find(parent[x]);
    return parent[x];
  }

  void merge(int x, int y) {
    x = find(x);
    y = find(y);
    parent[x] = y;
  }
};
class Solution {
public:
  int findCircleNum(vector<vector<int>>& isConnected) {
    int n = isConnected.size();
    UnionSet us(isConnected.size());

    for(int i = 0; i < n; ++i) {
      for(int j = 0; j < n; ++j) {
        if(i == j) continue;
        if(isConnected[i][j]) {
          us.merge(i, j);
        }
      }
    }

    set<int> st;
    for(int i = 0; i < n; ++i) {
      st.insert(us.find(i));
    }

    return st.size();
  }
};

// Accepted
// 113/113 cases passed (17 ms)
// Your runtime beats 97.38 % of cpp submissions
// Your memory usage beats 59.39 % of cpp submissions (13.9 MB)