PlusOne

问题描述：一个数组每一位代表一个数字的每一位。数字高位在数组的低位。求数字加1后得到新数组。

算法分析：要从数组的高位到低位进行遍历。

public class PlusOne
{
    public int[] plusOne(int[] digits) 
    {
        int len = digits.length;
        int carry = 0;
        digits[len-1] += 1;
        if(digits[len-1] >= 10)
        {
            digits[len-1] = digits[len-1]-10;
            carry = 1;
        }
        for(int i = len-2; i >=0 ; i --)
        {
            digits[i] += carry;
            if(digits[i] >= 10)
            {
                digits[i] = digits[i] - 10;
                carry = 1;
            }
            else
            {
                carry = 0;
            }
        }
        if(carry == 1)
        {
            int[] array = new int[len+1];
            for(int i = len; i > 0; i --)
            {
                array[i] = digits[i-1];
            }
            array[0] = 1;
            return array;
        }
        else
        {
            return digits;
        }
    }
     
    public int[] plusOne2(int[] digits) 
    {
        int n = digits.length;
        for(int i = n-1; i >=0; i --)
        {
            if(digits[i] < 9)
            {
                digits[i]++;
                return digits;
            }
            digits[i] = 0;
        } 
        int[] array = new int[n+1];
        array[0] = 1;
        return array;
    }
}