Plus One

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

    Example

    Given [9,9,9] which represents 999, return [1,0,0,0].

    2.     /**
    3.      * @return the result
    4.      */
    5.     public int[] plusOne(int[] digits) {
    6.         return plusDigit(digits, 1);
    7.     }
    9.     private int[] plusDigit(int[] digits, int digit) {
    12.         // regard digit(0~9) as carry
    13.         int carry = digit;
    14.         int[] result = new int[digits.length];
    15.         for (int i = digits.length - 1; i >= 0; i--) {
    16.             carry = (digits[i] + carry) / 10;
    17.         }
    20.         if (carry == 1) {
    21.             int[] finalResult = new int[result.length + 1];
    22.             finalResult[0] = 1;
    23.             return finalResult;
    24.         }
    26.         return result;
    27.     }
    28. }

    源码中单独实现了加任何数(0~9)的私有方法，更为通用，对于末尾第一个数，可以将要加的数当做进位处理，这样就不必单独区分最后一位了，十分优雅！