算法与数据结构---二分查找

def binary_sort(li, val):
    left = 0
    right = len(li) - 1
    while left <= right:
        mid = (left + right) // 2
        if li[mid] == val:
            return mid
        elif li[mid] < val:
            right = mid - 1
        else:
            left = mid + 1
    return None

l = [1, 3, 4, 5, 6]
print(binary_sort(l, 4))


# 内置查找函数index()---是线性查找
# 时间复杂度---O(logn)