almost-increasing-sequence.ts

export type Input = number[];
export type Output = boolean;

/**
 * Given a sequence of integers as an array, determine whether it is possible to obtain a strictly increasing sequence by removing no more than one element from the array.
 *
 * Note: sequence a0, a1, ..., an is considered to be a strictly increasing if a0 < a1 < ... < an.
 * Sequence containing only one element is also considered to be strictly increasing.
 *
 * Example:
 * - For sequence = [1, 3, 2, 1], the output should be solution(sequence) = false.
 * - There is no one element in this array that can be removed in order to get a strictly increasing sequence.
 *
 * - For sequence = [1, 3, 2], the output should be solution(sequence) = true.
 * - You can remove 3 from the array to get the strictly increasing sequence [1, 2]. Alternately, you can remove 2 to get the strictly increasing sequence [1, 3].
 *
 * @param sequence
 */
export const almostIncreasingSequence = (sequence: Input): Output => {
  let sequenceInterruptions = 0;

  for (let i = 1; i < sequence.length; i++) {
    if (sequence[i - 1] > sequence[i]) {
      sequenceInterruptions++;

      if (sequenceInterruptions > 1) return false;

      if (sequence[i - 1] >= sequence[i + 1] && sequence[i - 2] >= sequence[i])
        return false;
    }
  }

  return true;
};