算法与数据结构3之查找

def linear_search(li,val):  # 一个列表 一个待查找元素
    for ind,v in enumerate(li):
        if v == val:
            return ind
        else:
            return None

def binary_search(li,val):
    left = 0
    right = len(li) -1
    while left <= right:  #  候选区域
        mid = (left + right) // 2
        if li[mid] == val:
            return mid
        elif li[mid] > val:  # 待查找的值在mid左侧
            right = mid - 1
        else:               # li(mid) < val 待查找的值在mid右侧
            left = mid + 1
    else:
        return None

li = [1,2,3,4,5,6,7,8,9]
print(binary_search(li,3))

‘‘‘
时间复杂度O（logn)
‘‘‘

# cal_time.py文件代码

import time
def cal_time(func):
    def wrapper(*args,**kwargs):
        t1 = time.time()
        res = func(*args,**kwargs)
        t2 = time.time()
        print("%s runing time:%s secs."%(func.__name__,t2 - t1))
        return res
    return wrapper

###############  比较  ########################
from cal_time import *

@cal_time
def linear_search(li,val):  # 一个列表 一个待查找元素
    for ind,v in enumerate(li):
        if v == val:
            return ind
        else:
            return None

@cal_time
def binary_search(li,val):
    left = 0
    right = len(li) -1
    while left <= right:  #  候选区域
        mid = (left + right) // 2
        if li[mid] == val:
            return mid
        elif li[mid] > val:  # 待查找的值在mid左侧
            right = mid - 1
        else:               # li(mid) < val 待查找的值在mid右侧
            left = mid + 1
    else:
        return None

li = list(range(100000000))
linear_search(li,38900000)
binary_search(li,38900000)