Problems

Given a non-negative integer represented as a non-empty array of digits, plus one to the integer.

You may assume the integer does not contain any leading zero, except the number 0 itself.

The digits are stored such that the most significant digit is at the head of the list.

Solution

var plusOne = function(digits) {
    for(var i=digits.length-1; i>=0; i--) {
        if(digits[i]<9) {
            digits[i]++;
            return digits;
        } else {
            digits[i]=0;
        }
    }
};

Result

plusOne([1,2,3,4])  //[1, 2, 3, 5]

plusOne([1,2,5,9,9])   //[1, 2, 6, 0, 0]