66. Plus One.js

/*

You are given a large integer represented as an integer array digits, where each digits[i] is the ith digit of the integer.
The digits are ordered from most significant to least significant in left-to-right order. The large integer does not contain any leading 0's.

Increment the large integer by one and return the resulting array of digits.

 

Example 1:

Input: digits = [1,2,3]
Output: [1,2,4]
Explanation: The array represents the integer 123.
Incrementing by one gives 123 + 1 = 124.
Thus, the result should be [1,2,4].
Example 2:

Input: digits = [4,3,2,1]
Output: [4,3,2,2]
Explanation: The array represents the integer 4321.
Incrementing by one gives 4321 + 1 = 4322.
Thus, the result should be [4,3,2,2].
Example 3:

Input: digits = [9]
Output: [1,0]
Explanation: The array represents the integer 9.
Incrementing by one gives 9 + 1 = 10.
Thus, the result should be [1,0].
 

Constraints:

1 <= digits.length <= 100
0 <= digits[i] <= 9
digits does not contain any leading 0's.

*/

/**
 * @param {number[]} digits
 * @return {number[]}
 */
var plusOne = function(digits) {
    // [9,9,9,9,9,9]
    let rest = digits.at(-1) === 9 ? 1 : 0;

    if (rest === 0) {
      digits[digits.length - 1] += 1;
      return digits;
    }

    for (let i = digits.length - 1; rest === 1 && i >= 0; i--) {
      digits[i] += rest;
      rest = 0;
      if (digits[i] === 10) {
        rest = 1;
        digits[i] = 0;
      }
    }
    if (rest === 1) {
      return [1, ...digits];
    }

    return digits;
};