查询算法-二分查找

alist = [1, 2, 3, 4, 5, 6, 7, 8]

def binarySearch(alist, target):
    first = 0
    last = len(alist) - 1
    while first <= last:
        middle_index = (first + last) // 2
        if target > alist[middle_index]:
            first = middle_index + 1
        elif target < alist[middle_index]:
            last = middle_index - 1
        else:
            return middle_index
    return -1

ret=binarySearch(alist,5)
print(ret)