PlusOne.java

class PlusOne {
    public int[] plusOne(int[] digits) {
        
        int carry = 1;
        
        for (int i = digits.length-1; i>= 0; i--) {
         
            digits[i] += carry;
            
            if (digits[i] <= 9)         // if no carry generated then early return 
                return digits;
            
            digits[i] = 0;
        }
        
        int[] ret = new int[digits.length+1];
        ret[0] = 1;
        
        return ret;
    }
}