Plus One

plusOne.java

/*
Given a number represented as an array of digits, plus one to the number.
*/
public class Solution {
    public int[] plusOne(int[] digits) {
        // Start typing your Java solution below
        // DO NOT write main() function
        int len = digits.length - 1;
        digits[len] = digits[len] + 1;
        int carry = digits[len] >= 10 ? 1 : 0;
        // check if the last digit + 1 > 10
        while(carry > 0 && len > 0)  {
            // get the single digit for the position len
            digits[len] = digits[len] - 10;
            len--;
            // add the carry to higher digit
            digits[len] += carry;
            carry = digits[len] >= 10 ? 1 : 0;
        }
        
        // check and make sure the each digit is < 10
        if(digits[len] >= 10) digits[len] -= 10;
        int[] ret = new int[digits.length+carry];
        ret[len] = carry;
        int fLen = digits.length+carry-1;
        for(int i = digits.length-1; i>=0; i--) {
            // copy over the digits to the ret
            ret[fLen] = digits[i];
            fLen--;
        }
        return ret;
    }
}