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var sortEvenOdd = function (nums) {
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  let odd = nums.filter((num, i, arr) => i % 2 != 0).sort((a, b) => b - a); //decreasing order
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  let even = nums.filter((num, i, arr) => i % 2 == 0).sort((a, b) => a - b); //increasing order
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  let x = 0,
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    y = 0;
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  nums.forEach((num, i, nums) => {
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    nums[i] = i % 2 == 0 ? even[x++] : odd[y++]; //refilling the array
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  });
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  return nums;
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};