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Copy path547_friend_circles.py
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103 lines (83 loc) · 2.35 KB
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from typing import List
class Solution:
def findCircleNum(self, M: List[List[int]]) -> int:
count = 0
n = len(M)
visited = set()
def dfs(i):
for j in range(0, n):
if j not in visited and M[i][j]:
visited.add(j)
dfs(j)
for i in range(n):
if i not in visited:
visited.add(i)
count += 1
dfs(i)
return count
def findCircleNum2(self, M: List[List[int]]) -> int:
count = 0
n = len(M)
visited = set()
for i in range(n):
if i not in visited:
visited.add(i)
queue = [i]
count += 1
while queue:
k = queue.pop(0)
for j in range(0, n):
if j not in visited and M[k][j]:
visited.add(j)
queue.append(j)
return count
def findCircleNum3(self, M: List[List[int]]) -> int:
n = len(M)
count = n
parent = list(range(n))
size = [1] * n
def find(i):
while i != parent[i]:
parent[i] = parent[parent[i]] # compress path
i = parent[i]
return i
def union(i, j):
nonlocal count
pi = find(i)
pj = find(j)
if pi == pj:
return
if size[pi] > size[pj]:
parent[pj] = pi
size[pi] += size[pj]
else:
parent[pi] = pj
size[pj] += size[pi]
count -= 1
for i in range(n):
for j in range(i + 1, n):
if M[i][j]:
union(i, j)
return count
def test():
examples = [
([[1, 1, 1], [1, 1, 1], [1, 1, 1]], 1),
([
[1, 0, 0, 1],
[0, 1, 1, 0],
[0, 1, 1, 1],
[1, 0, 1, 1]
], 1),
([[1, 1, 0],
[1, 1, 1],
[0, 1, 1]], 1),
([[1, 1, 0],
[1, 1, 0],
[0, 0, 1]], 2)
]
s = Solution()
for (m, expect) in examples:
ans = s.findCircleNum3(m)
assert ans == expect, f"expect {expect}, got {ans}"
if __name__ == "__main__":
test()