列表查询算法

列表二分查询 & 遍历查询 & 递归二分

1、二分查找复杂度：O(logn)
2、遍历查询复杂度：O(n)

def common_search(lst,n):
    """遍历超找"""
    for item in lst:
        if item==n:
            return n
    return '未找到'


def bin_search(lst, n):
    """二分法查找，根据中间数改变索引即可"""
    low_index = 0
    high_index = len(lst)-1
    while low_index<=high_index:
        mid = (low_index + high_index) // 2
        if lst[mid] > n:
            high_index=mid-1

        elif n == lst[mid]:
            return mid

        else:
            low_index=mid+1

    return '没到找'


def bin_search_recur(lst,n,low,high):
    """方法同上，采用递归"""
    mid = (low+high)//2
    if low<=high:
        if lst[mid]>n:
            return bin_search_recur(lst,n,low,mid-1)
        elif n == lst[mid]:
            return mid
        else:
            return bin_search_recur(lst, n, mid+1, high)
    return None


import time
start_time = time.time()

lst = list(range(10000000))
# bin_search(lst,9999900)
# common_search(lst,9999900)
bin_search_recur(lst,9999900,0,9999999)

end_time = time.time()

print('耗时：%s' % (end_time-start_time))

# 二分查询耗时：0.21814703941345215
# 遍历查找耗时：0.9246125221252441
# 二分递归耗时：0.23915982246398926