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Plus One

Problem

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

/**
* @param {number[]} digits
* @return {number[]}
*/
var plusOne = function(digits) {
digits[digits.length - 1]++;
for (let i = digits.length - 1; i >= 1; --i) {
if (digits[i] === 10) {
digits[i] = 0;
digits[i - 1]++;
} else {
break;
}
}
if (digits[0] === 10) {
digits[0] = 0;
digits.unshift(1);
}
return digits;
};

Add 1 to the last digit. If the digit becomes 10, carry over 1 and repeat. The only edge case is when the first digit has value 10, so the carry over must be pushed to the front of the array.