Simple Python DFS

  • 0

    DFS search each friend chain then record all visited friends for each run. Increment counter only if an unvisited friend is discovered, as this indicates the start of a new chain

        def findCircleNum(self, M):
            processed = set()
            cnt = 0
            for r in range(len(M)): 
                if r not in processed:
                    cnt += 1
                    stack = [i for i,v in enumerate(M[r]) if i != r and v == 1]
                    while stack:
                        curr = stack.pop()
                        if curr in processed: continue
                        stack.extend([i for i,v in enumerate(M[curr]) if i != r and v == 1])
            return cnt

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