二分查找

内置模块bisect.bisect实现二分查找， bisect.insort二分插入

def bisect_right(iterable, search_value, lo=0, hi=None):
    """Return the index where to insert item search_value in list iterable, assuming iterable is sorted.
    """

    if lo < 0:
        raise ValueError('lo must be non-negative')
    if hi is None:
        hi = len(iterable)
    while lo < hi:
        mid = (lo+hi)//2
        if search_value < iterable[mid]:
            hi = mid
        else:
            lo = mid+1
    return lo

 

自己写一个二分查找：

def bin_search(li, val):
    low = 0
    high = len(li) - 1
    while low <= high:
        mid = (low + high) // 2
        if li[mid] == val:
            return mid
        elif li[mid] > val:
            high = mid - 1
        else:
            low = mid + 1
    return None