[to be continued] [depth first search] 547 Number of provinces

One 、 subject

Yes n Cities , Some of them are connected to each other , Others are not connected . If the city a And the city b Direct connection , And the city b And the city c Direct connection , So the city a And the city c Indirectly connected .

Province It's a group of directly or indirectly connected cities , There are no other cities in the group that are not connected .

To give you one n x n Matrix isConnected , among isConnected[i][j] = 1 It means the first one i Two cities and j The two cities are directly connected , and isConnected[i][j] = 0 The two are not directly connected .

Back in the matrix Province The number of .

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

Two 、 Answer key

3、 ... and 、 Code