1
var validSquare = function (p1, p2, p3, p4) {
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  const distance = (a, b) => {
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    const [aX, aY] = a;
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    const [bX, bY] = b;
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    return (aX - bX) ** 2 + (aY - bY) ** 2;
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  };
7

8
  const set = new Set([
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    distance(p1, p2),
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    distance(p1, p3),
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    distance(p1, p4),
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    distance(p2, p3),
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    distance(p2, p4),
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    distance(p3, p4),
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  ]);
16

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  return !set.has(0) && set.size === 2;
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};