Number of Provinces

# Number of Provinces You're given an `n x n` adjacency matrix `is_connected` where `is_connected[i][j] == 1` means city `i` and city `j` are directly connected. A **province** is a group of directly or indirectly connected cities. Return the number of provinces. Same connected-components idea as Module 1's graph BFS/DFS lesson, but on an adjacency-**matrix** input rather than the grid input Mock 4 uses — a genuinely different graph representation to exercise. **Example:** `[[1,1,0],[1,1,0],[0,0,1]]` -> `2`. Target complexity: O(N²) time.