我有一个助手。 assingment说要在python中编写两个函数:
我的第一个功能 - sort
- 可以排序。但是,我的第二个功能是没有正确执行二进制搜索。我的最终目标是结合这两个功能。
这是我目前的代码:
冒泡排序
def sort(x):
for j in range(len(x)):
for i in range (len(x)-1):
if x[i]> x[i+1]:
temp =x[i]
x[i]=x[i+1]
x[i+1]=temp
return x
sl = sort([87,56,34,23,89,15,2,200,28,31])
print (sl)
二进制搜索
def bs(t):
s = 0
e = len(t)-1
found = False
c = int(input("Enter"))
while (s<=e):
mid = (s+e)//2
if t[mid]==c:
found = True
elif c > t[mid]:
s = mid+1
else:
e = mid-1
return found
bs([1,2,3,4,5])
答案 0 :(得分:1)
问题出在你的while
循环中。如果找到项目s
或e
没有增加/减少,循环变为无限。
您应该添加break
语句或拆分if
条件:
def bs(t):
t = sort(t)
s = 0
e = len(t)-1
found = False
c = int(input("Enter"))
while (s<=e):
mid = (s+e)//2
if t[mid]==c:
found = True
break
elif c > t[mid]:
s = mid+1
else:
e = mid-1
return found
bs([1,2,3,4,5])
或:
def bs(t):
t = sort(t)
s = 0
e = len(t)-1
found = False
c = int(input("Enter"))
while (s<=e):
mid = (s+e)//2
if t[mid]==c:
found = True
if c > t[mid]:
s = mid+1
else:
e = mid-1
return found
bs([1,2,3,4,5])
组合功能(sort + bs):
def binary_search(x):
for j in range(len(x)):
for i in range(len(x) - 1):
if x[i] > x[i + 1]:
temp = x[i]
x[i] = x[i + 1]
x[i + 1] = temp
s = 0
e = len(x)-1
found = False
c = int(input("Enter"))
while s <= e:
mid = (s + e)//2
if x[mid] == c:
found = True
break
elif c > x[mid]:
s = mid+1
else:
e = mid-1
return found
结合一些重构:
def binary_search(x):
# j is not used, so it could be replaced with underscore
for _ in range(len(x)):
for i in range(len(x)-1):
if x[i] > x[i+1]:
# this is illustration of python awesomeness
x[i], x[i+1] = x[i+1], x[i]
c = int(input("Enter"))
while x:
# this line is actually the same as s + e, because
# is always equals to list's len - 1
mid = (len(x)-1)//2
# instead of redefining variable - just break from loop
if x[mid] == c:
break
if c > x[mid]:
# slice list instead of computing new start index
x = x[mid+1:]
else:
# slice list instead of computing new last index
x = x[:mid-1]
return len(x) > 0 # true if x contains at least one el and false otherwise
sl = binary_search([87, 56, 34, 23, 89, 15, 2, 200, 28, 31])
print(sl)