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var trap = function (height) {
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  let landArea = 0;
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  let maxFromLeft = 0;
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  let maxAreaFromLeft = 0;
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  for (let h of height) {
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    landArea += h;
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    maxFromLeft = Math.max(maxFromLeft, h);
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    maxAreaFromLeft += maxFromLeft;
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  }
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  let maxFromRight = 0;
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  let maxAreaFromRight = 0;
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  for (let i = height.length - 1; i >= 0; i--) {
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    maxFromRight = Math.max(maxFromRight, height[i]);
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    maxAreaFromRight += maxFromRight;
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  }
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  const boundingArea = height.length * maxFromLeft;
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  const leftVoid = boundingArea - maxAreaFromLeft;
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  const rightVoid = boundingArea - maxAreaFromRight;
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  return boundingArea - leftVoid - rightVoid - landArea;
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};