python 代码实现二分查找（非递归版本）

def binary_search(alist, item):
    '''二分查找'''
    n = len(alist)
    first = 0
    last = n -1
    while first <= last:
        mid = (first+last)//2#中间位置下标获取很关键
        if alist[mid] == item:
            return True
        elif item < alist[mid]:
            last = mid-1
        else:
            first = mid +1
    return False

if __name__ == '__main__':
    li = [0, 5, 8, 10, 65, 99, 100]
    print(binary_search(li, 99))
    print(binary_search(li, -1))

C:\Users\user\AppData\Local\Programs\Python\Python36\python.exe “C:/Users/user/PycharmProjects/hellow python/test.py”
True
False

Process finished with exit code 0