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binary_search.py
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"""
@version: python3.6
@author: Fieldhunter
@contact: [email protected]
@time: 2020-05-03
"""
def binary_search(data_list, target):
num = len(data_list)
low = 0
high = num - 1
find = False
while low <= high:
middle_num = low + (high-low) // 2
if data_list[middle_num] == target:
find = True
break
elif data_list[middle_num] < target:
low = middle_num + 1
else:
high = middle_num - 1
if find:
print(middle_num)
else:
print("No data")
# Find the element whose first value is equal to the target
def binary_search_1(data_list, target):
num = len(data_list)
low = 0
high = num - 1
find = False
while low <= high:
middle_num = low + (high-low) // 2
if data_list[middle_num] == target:
find = True
if middle_num == 0 or data_list[middle_num-1] != target:
break
else:
high = middle_num - 1
elif data_list[middle_num] < target:
low = middle_num + 1
else:
high = middle_num - 1
if find:
print(middle_num)
else:
print("No data")
# Find the element whose last value is equal to the target
def binary_search_2(data_list, target):
num = len(data_list)
low = 0
high = num - 1
find = False
while low <= high:
middle_num = low + (high-low) // 2
if data_list[middle_num] == target:
find = True
if middle_num == num - 1 or data_list[middle_num+1] != target:
break
else:
low = middle_num + 1
elif data_list[middle_num] < target:
low = middle_num + 1
else:
high = middle_num - 1
if find:
print(middle_num)
else:
print("No data")
# Find the first element greater than or equal to the target
def binary_search_3(data_list, target):
num = len(data_list)
low = 0
high = num - 1
find = False
while low <= high:
middle_num = low + (high-low) // 2
if data_list[middle_num] < target:
low = middle_num + 1
elif middle_num == 0 or data_list[middle_num-1] < target:
find = True
break
else:
high = middle_num - 1
if find:
print(middle_num)
else:
print("No data")
# Find the last element less than or equal to the target
def binary_search_4(data_list, target):
num = len(data_list)
low = 0
high = num - 1
find = False
while low <= high:
middle_num = low + (high-low) // 2
if data_list[middle_num] > target:
high = middle_num - 1
elif middle_num == num - 1 or data_list[middle_num+1] > target:
find = True
break
else:
low = middle_num + 1
if find:
print(middle_num)
else:
print("No data")