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from collections import defaultdict
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class Solution:
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    def minReorder(self, n: int, connections: List[List[int]]) -> int:
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        count, stack, visited = 0, [0], set()  # Add root node to stack
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        neighbours = defaultdict(list)  # To store neighbours
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        adjacency = defaultdict(list)  # To store adjacency
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        for i, j in connections:
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            adjacency[i].append(j)
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            neighbours[i].append(j)
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            neighbours[j].append(i)
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        while stack:
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            current = stack.pop()
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            if current in visited:
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                continue
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            else:
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                visited.add(current)
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            for i in neighbours[current]:
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                if i in visited:
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                    continue
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                if current not in adjacency[i]:
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                    count += 1
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                stack.append(i)
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        return count