Plus One

Description

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.

Solution(javascript)

/**
 * @param {number[]} digits
 * @return {number[]}
 */
var plusOne = function(digits) {
   // iterate through the array from last element to first
    for (let i = digits.length - 1; i >= 0; i--) {
        // increment the element
        digits[i]++;
        // if element is less than 10 and not the leftmost element, end iteration and return the array
        if (digits[i] < 10 && digits[i] !== 0) return digits;
        // element must be >10, so decrease by 10. No need to create a "carry" variable, because each               iteration assumes the element needs to be incremented.
        digits[i] = 0;
        // if this is the leftmost element, we need to add one more element to the left to catch the                carry
        if (i === 0) {
            digits.unshift(1)
            return digits;
        }
    }
};