Graph Exploration Target: 15s
Loop over all nodes, DFS/BFS from unvisited ones, increment count each time. Works on adjacency list or matrix.
visited = set()
count = 0
for node in range(n):
if node not in visited:
count += 1
stack = [node]
while stack:
cur = stack.pop()
if cur in visited: continue
visited.add(cur)
stack.extend(graph[cur])Type it from memory. Go.