findNumberSequence.js

/**
In a game, there is a string, direction, of length n that consists of characters
L and R.
L denotes left. R denotes right, and there is a line segment of
length 2" that extends from [0, 2"], a player takes n turns.
In the th turn,
• The player places the number i at the center of the current line segment.
• If direction[i] = L; the player proceeds in the left direction, eliminating the right half of the current line segment,
and vice versa for direction[i] = 'R'.
Following this rule, find the final order of numbers on the line segment,
starting from the left.
Example direction = "LRRLLL".
There are n = 6 characters in the initial length of the line segment.
The segment length is 2" = 2" = 64 in the range [0, 64].
 */
function findNumberSequence(direction) {
  const n = direction.length;
  const result = [];
  let lower = 0;
  let higher = 2 ** n; // Math.pow(2, n);

  for (let i = 0; i < n; i += 1) {
    const center = Math.floor((lower + higher) / 2);
    result[center] = i + 1;

    if (direction[i] === 'L') {
      higher = center - 1;
    } else {
      lower = center + 1;
    }
  }

  return result.filter(num => num !== undefined);
}

const direction = 'LRRLLL';
const result = findNumberSequence(direction);
console.log(result); // output: [2, 4, 5, 6, 3, 1]

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