The principle of common search algorithm and Python implementation

• Sequential Lookup
• Two-point Search
• Practice

First, sequential search

Data=[1,3,4,5,6]value=1def Linear_search (data,value):    flag=false for    i in range (0,len (data)):        if Data[i ]==value:            # return I            flag=true            print (' found at%s position '%i)    if not flag:        print (' Find failed ') # Linear_search (Data,value)

Two or two points find

Recursion: (not high efficiency)

Recursion requires an end condition (len (data) <=1), and each recursive problem is reduced in size

Change is the data that is passed in every

#递归实现def Bin_search2 (data,value):    mid=len (data)/2    If Len (data) >1:        if Value>data[mid]:            bin_ SEARCH2 (data[mid+1:],value)        elif Value<data[mid]:            bin_search2 (Data[0:mid-1],value)        else:            Return mid    else:        if Data[0]==value:            return 0        else:            print (' Find failed ')

Non-recursive:

Change the direction of the low and high pointers

def bin_search (data,value):     flag=false     low=0     high=len (data)-1 while     Low<=high:         mid= ( Low+high)//2         if Value>data[mid]:             low=mid+1         elif value<data[mid]:             high=mid-1         Else:             flag=true             return mid     if not flag:         print (' Find failed ') print (Bin_search (data,value))

Third, practice

#练习info =[    {"id": 1001, "name": "Zhang San", "Age": $},    {"id": 1002, "name": "John Doe", "Age": [],    {"id": 1004, "name": " Harry "," Age ": +},    {" id ": 1007," name ":" Zhao Liu "," Age ": 33}]def Bin_search (data,value):    low=0    High=len (data)-1    while Low<=high:        mid= (low+high)//2        if data[mid][' id ']==value: #取字典的value with Dic[key]            return (Mid, Data[mid])        elif data[mid][' id ']<value:            low=mid+1        Else:            high=mid-1    Else:        return (0,none) #根据返回值判断是否查到这个人while True:    id=int (Input (' Please enter the number you want to find (Exit press Q): '). Strip ())    # print (Type (ID)    ) If id== ' Q ':        break    Else:        num,info=bin_search (info,id)        if info== ' None ':            print (' No this person ')        Else:            print (' info:%s '%info)

　　

The principle of common search algorithm and Python implementation