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To give an example of a topology on a set of four points, different from discrete and anti-discrete, in which every open set is closed, and every closed set is open.I have 0 ideas at all, I thought that just the same, that only a discrete topology has such characteristics for sets.

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$$\mathcal{T} = \{\varnothing, \{a, b\}, \{c, d\}, \{a, b, c, d\}\}$$

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  • $\begingroup$ This question doesn’t meet the standards for the site. Instead of answering it (which encourages low-quality questions), why not look for a good duplicate target, or help the user by posting comments suggesting improvements? Please also read the meta announcement regarding quality standards. $\endgroup$ Commented May 25 at 7:38

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