[leetcode:python]66.Plus One

题目：

Given a non-negative integer represented as a non-empty array of digits, plus one to the integer.

You may assume the integer do not contain any leading zero, except the number 0 itself.

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

题意：

给定一个非负数，用非空数组表示，对这个非负数加一，把和存到这个数组。

方法一：性能46ms

class Solution(object):
def plusOne(self, digits):
"""
:type digits: List[int]
:rtype: List[int]
"""
digits[-1] += 1
if digits[-1] < 10:
return digits
s = []
while digits[-1] == 10:
s.append(0)
digits.pop()
if len(digits) == 0:
s[0] = 1
s.append(0)
return s
digits[-1] += 1
while s:
digits.append(s.pop(0))
return digits

方法二：性能35ms

class Solution(object):
def plusOne(self, digits):
"""
:type digits: List[int]
:rtype: List[int]
"""
for i in xrange(len(digits)-1, -1, -1):
if digits[i]<9:
digits[i] = digits[i] + 1;
return digits;
else:
digits[i] = 0;
if digits[0] == 0:
digits.insert(0,1);
return digits;