Python implements a binary algorithm example

1. Algorithm :(set the period of the array searched as array[low, high])

(1) determine the intermediate position K during the period
(2) compare the value T to array[k]. If equal, the search returns this position; Otherwise, determine a new search area and continue binary search. The region is determined as follows:

A.a rray [k] > Array [k,k+1... high] > T; So the new interval is array[low... K-1]
B.a rray [k] < T is similar to the search interval above for array[k+1,..., high]. Each time the search and the middle value comparison, you can determine whether the search is successful, not successful the current search interval reduced by half. Recursively.

#!/usr/bin/python

# -*- coding: utf-8 -*-
def BinarySearch(array,t):

low = 0

height = len(array)-1

while low <= height:

mid = (low+height)/2

if array[mid] < t:

low = mid + 1
elif array[mid] > t:

height = mid - 1
else:

return array[mid]
return -1
if __name__ == "__main__":

print BinarySearch([1,2,3,34,56,57,78,87],57)

Results: 57

3. Time complexity :O(log2n);

Note: the premise of binary search must wait for the search sequence to be ordered.