Submission #8424245

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Source Code Expand

import sys
input = sys.stdin.readline


class UnionFind():
    def __init__(self, n):
        self.n = n
        self.parents = [-1] * n

    def find(self, x):
        if self.parents[x] < 0:
            return x
        else:
            self.parents[x] = self.find(self.parents[x])
            return self.parents[x]

    def union(self, x, y):
        x = self.find(x)
        y = self.find(y)
        if x == y:
            return
        if self.parents[x] > self.parents[y]:
            x, y = y, x
        self.parents[x] += self.parents[y]
        self.parents[y] = x

    def size(self, x):
        return -self.parents[self.find(x)]

    def same(self, x, y):
        return self.find(x) == self.find(y)

    def members(self, x):
        root = self.find(x)
        return [i for i in range(self.n) if self.find(i) == root]

    def roots(self):
        return [i for i, x in enumerate(self.parents) if x < 0]

    def group_count(self):
        return len(self.roots())

    def all_group_members(self):
        return {r: self.members(r) for r in self.roots()}

    def __str__(self):
        return '\n'.join('{}: {}'.format(r, self.members(r)) for r in self.roots())


def main():
    N, M = map(int, input().split())
    P = list(map(int, input().split()))
    uf = UnionFind(N+1)
    for i in range(M):
        x, y = map(int, input().split())
        uf.union(x, y)
    ans = 0
    for r in uf.roots():
        ms = uf.members(r)
        p = set()
        for m in ms:
            p.add(P[m-1])
#        print(p, ms)
        ans += len(p & set(ms))
    print(ans)


if __name__ == '__main__':
    main()

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