python反转列表_python列表反转
使用reverse來讓列表反轉(zhuǎn)特別方便, 沒事自己寫了幾種方式
In [59]: def reverse(nums):
length = len(nums)
for i in range(length-1):
nums.insert(length-i-1, nums.pop(0))
print nums
....:
In [60]:
In [60]:
In [60]: a = range(5)
In [61]: reverse(a)
[1, 2, 3, 4, 0]
[2, 3, 4, 1, 0]
[3, 4, 2, 1, 0]
[4, 3, 2, 1, 0]
In [62]: a
Out[62]: [4, 3, 2, 1, 0]
In [63]:
根據(jù)結(jié)果能看出, insert操作的執(zhí)行順序是先刪除, 后插入
In [67]: def reverse(nums):
i, j = 0, len(nums)-1
while i < j:
nums[i], nums[j] = nums[j], nums[i]
i, j = i+1, j-1
print nums
In [69]: a = range(5)
In [70]: a
Out[70]: [0, 1, 2, 3, 4]
In [71]:
In [71]: reverse(a)
[4, 1, 2, 3, 0]
[4, 3, 2, 1, 0]
In [72]: a
Out[72]: [4, 3, 2, 1, 0]
In [73]:
以上兩種都是原地操作
In [78]: a
Out[78]: [0, 1, 2, 3, 4]
In [79]:
In [79]: b = []
In [80]: def reverse(nums):
....: for i in nums:
....: b.insert(0, i)
....:
In [81]:
In [81]: reverse(a)
In [82]:
In [82]: b
Out[82]: [4, 3, 2, 1, 0]
In [83]: id(a)
Out[83]: 140434157093160
In [84]: id(b)
Out[84]: 140434157062984
In [85]:
總結(jié)
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