[leetcode] 547. Number of Provinces _ Algorithm Problem Solve for python

1. Problem

547. 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]

2. Solution

I solved this problem like this.

I sovled this problem using dfs. If dfs method called, plus 1 on provinces.

class Solution:
    def findCircleNum(self, isConnected: List[List[int]]) -> int:
        provinces = 0
        visited = [0] * len(isConnected)
        n = len(isConnected)

        def dfs(idx):
            if visited[idx]:
                return
            visited[idx] = 1

            for i in range(n):
                if isConnected[idx][i]:
                    dfs(i)

        for i in range(n):
            if not visited[i]:
                dfs(i)
                provinces += 1

        return provinces