python--二分查找

***搜索过程从数组的中间元素开始，如果中间元素正好是要查找的元素，则搜索过程结束；如果某一特定元素大于或者小于中间元素，则在数组大于或小于中间元素的那一半中查找，而且跟开始一样从中间元素开始比较。如果在某一步骤数组为空，则代表找不到。这种搜索算法每一次比较都使搜索范围缩小一半***

# @param array: The integer array
# @param key: Target number to find
# @return the first position of target in nums, position start from 0

def binarySearch(array, key):
array_len = len(array)
if array_len == 0 or array_len == 1:
return 0 if key in array else -1
low = 0
heigh = array_len - 1

while low < heigh:
mid = (heigh + low) // 2
if array[mid] < key:
low = mid + 1
elif array[mid] > key:
heigh = mid - 1
else:
res = mid
break
else:
res  = low if array[low] == key else -1
while(res>=0):
tem = res-1
if array[res]==array[tem]:
res = tem
else:
break
return res