Solution.py

"""

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]


"""


class Solution:
    def findCircleNum(self, M: List[List[int]]) -> int:
        visited = set()
        cnt = 0
        for i in range(len(M)):
            if i in visited:
                continue
            cnt += 1
            stack = [i]
            while stack:
                curr = stack.pop()
                visited.add(curr)
                for j in range(len(M)):
                    if M[curr][j] == 1 and j not in visited:
                        stack.append(j)
            if len(visited) == len(M):
                break
        return cnt