python---二分查找的实现

from cal_time import get_running_time

@get_running_time
def bin_search(li, val):
    """
    二分查找

    :param li: 要查找的有序列表
    :param val: 要查找的值
    :return:
    """

    n = len(li)
    low = 0
    high = n - 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 -1

def bin_search_rec(li, val, low, high):
"""
    二分查找递归版

    :param li: 要查找的列表
    :param val: 要查找的值
    :param low: 候选区域起始位置
    :param high: 候选区域结束位置
    :return:
    """

    if low <= high:

        mid = (low + high) // 2

        if li[mid] == val:
            return mid
        elif li[mid] > val:
            return bin_search_rec(li, val, low, mid-1)
        else:
            return bin_search_rec(li, val, mid+1, high)

    return -1

@get_running_time
def b_search_r(li, val, low, high):
    return bin_search_rec(li, val, low, high)