Plus One

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 carry = 0;
        boolean sig = false;
        int[] result = null;
        if(digits == null) return null;
        for(int i = 0;i < digits.length; i ++){
            if(digits[i] != 9) sig = true;
        }
        if(sig == false){
            result = new int[digits.length + 1];
            result[0] = 1;
            return result;
        }else{
            result = new int[digits.length];
            result[digits.length - 1] = digits[digits.length - 1] + 1;
            if(result[digits.length - 1] > 9){
                result[digits.length - 1] -= 10;
                carry = 1;
            }
            for(int i = digits.length - 2; i > -1; i --){
                result[i] = digits[i] + carry;
                if(result[i] > 9){
                    result[i] -= 10;
                    carry = 1;
                }else{
                    carry = 0;
                }
            }
            return result;
        }
    }
}

 Second Round:

public class Solution {
    public int[] plusOne(int[] digits) {
        boolean sig = false;
        for(int i = 0; i < digits.length; i ++)
            if(digits[i] != 9) sig = true;
        if(!sig){
            int[] result = new int[digits.length + 1];
            result[0] = 1;
            return result;
        }
        int[] result = new int[digits.length];
        int carry = 1;
        for(int i = digits.length - 1; i > -1; i --){
            result[i] = (digits[i] + carry) % 10;
            carry = (digits[i] + carry) / 10;
        }
        return result;
    }
}