為什么只是以不同的順序或風格撰寫代碼會改變整體運行時？
例如：
為什么 is
result = "1"比 快result = "1" result？
更詳細的例子：
為這個 Leetcode 問題撰寫成功的程式后 -添加二進制
在這里，我有兩個相同的代碼片段，但有一個非常微妙的區別。
代碼 1
def addBinary(a, b):
max_len = max(len(a), len(b))
a = a.zfill(max_len)
b = b.zfill(max_len)
result = ""
carry = 0
for i in range(len(a)-1, -1, -1):
x = int(a[i])
y = int(b[i])
_sum = x y carry
if _sum == 3:
result = "1"
carry = 1
elif _sum == 2:
result = "0"
carry = 1
elif _sum == 1:
result = "1"
carry = 0
else:
result = "0"
carry = 0
if carry == 1:
result = "1"
return result[::-1]
代碼 2
def addBinary(a, b):
max_len = max(len(a), len(b))
a = a.zfill(max_len)
b = b.zfill(max_len)
result = ""
carry = 0
for i in range(len(a)-1, -1, -1):
x = int(a[i])
y = int(b[i])
_sum = x y carry
if _sum == 3:
result = "1" result
carry = 1
elif _sum == 2:
result = "0" result
carry = 1
elif _sum == 1:
result = "1" result
carry = 0
else:
result = "0" result
carry = 0
if carry == 1:
result = "1"
return result
CODE 1的運行時間是16 ms，而CODE 2的運行時間是47 ms。為什么？
uj5u.com熱心網友回復：
Adding characters to the end is optimised internally to reuse the same string (array of characters) in memory. Adding at the beginning requires creating a new string, with the position of each character shifted.
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