717. 1-bit and 2-bit Characters

Description

We have two special characters:

The first character can be represented by one bit 0.
The second character can be represented by two bits (10 or 11).

Given a binary array bits that ends with 0, return true if the last character must be a one-bit character.

Example 1:

Input: bits = [1,0,0]
Output: true
Explanation: The only way to decode it is two-bit character and one-bit character.
So the last character is one-bit character.

Example 2:

Input: bits = [1,1,1,0]
Output: false
Explanation: The only way to decode it is two-bit character and two-bit character.
So the last character is not one-bit character.

Constraints:

1 <= bits.length <= 1000
bits[i] is either 0 or 1.

Solutions

Solution: Greedy

Time complexity: O(n)
Space complexity: O(1)

JavaScript

js

/**
 * @param {number[]} bits
 * @return {boolean}
 */
const isOneBitCharacter = function (bits) {
  const n = bits.length;
  let index = 0;

  while (index < n - 1) {
    index += bits[index] ? 2 : 1;
  }

  return bits[index] === 0;
};