Plus One/ code 13

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本文介绍了解决数组加一问题的两种方法。方法一是通过遍历数组并处理特殊情况来实现；方法二是将数组转换为整数，进行加一操作后再转回数组形式。这两种方法各有特点，适用于不同的场景。

Given a non-empty array of digits representing a non-negative integer, plus one to the integer.
The digits are stored such that the most significant digit is at the head of the list, and each element in the array contain a single digit.
You may assume the integer does not contain any leading zero, except the number 0 itself.
Example 1:
Input: [1,2,3] Output: [1,2,4]
Explanation: The array represents the integer 123.
Example 2:
Input: [4,3,2,1] Output: [4,3,2,2]

Explanation: The array represents the integer 4321.

code1 :

class Solution(object):
def plusOne(self, digits):
"""
:type digits: List[int]
:rtype: List[int]
"""
index = len(digits)-1
if digits[index] != 9:
digits[index] += 1
else:
digits[index] = 10
while(digits[index] == 10 and index > 0):
digits[index] = 0
index -= 1
digits[index] += 1
if digits[index] == 10:
digits[index] = 0
digits.insert(0,1)

return digits

code 2:

class Solution(object):
def plusOne(self, digits):
"""
:type digits: List[int]
:rtype: List[int]
"""
num = 0
for i in range(len(digits)):
num += digits[i] * pow(10, (len(digits)-1-i))

return [int(i) for i in str(num+1)]

笔记：方法1是针对各种特殊情况，进行计算。

方法2 是先把list转化为整数，然后加一之后又转化为字符取最后一个数字

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