1
var sumSubseqWidths = function (nums) {
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  const mod = 1000000007;
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  nums.sort((a, b) => a - b), (total = 0), (power = 1);
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  for (let i = 0; i < nums.length; i++) {
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    total = (total + nums[i] * power) % mod;
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    power = (power * 2) % mod;
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  }
8

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  power = 1;
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  for (let i = nums.length - 1; i >= 0; i--) {
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    total = (total - nums[i] * power + mod) % mod;
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    power = (power * 2) % mod;
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  }
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  return (total + mod) % mod;
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};