leetcode_solutions/constructDistancedSequence.js at main · TheCaptain1810/leetcode_solutions · GitHub

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/**
 * @param {number} n
 * @return {number[]}
 */
var constructDistancedSequence = function (n) {
  let result = Array(2 * n - 1).fill(0);
  let used = Array(n + 1).fill(false);
  backtrack(result, used, n, 0);
  return result;
};

function backtrack(result, used, n, index) {
  while (index < result.length && result[index] !== 0) {
    index++;
  }
  if (index === result.length) {
    return true;
  }

  for (let i = n; i >= 1; i--) {
    if (used[i]) continue;

    if (i === 1) {
      result[index] = 1;
      used[1] = true;
      if (backtrack(result, used, n, index + 1)) return true;
      result[index] = 0;
      used[1] = false;
    } else if (index + i < result.length && result[index + i] === 0) {
      result[index] = i;
      result[index + i] = i;
      used[i] = true;
      if (backtrack(result, used, n, index + 1)) return true;
      result[index] = 0;
      result[index + i] = 0;
      used[i] = false;
    }
  }
  return false;
}