Python查找算法

顺序查找

# sequential search
def sequential(ls,value):
    for i in range(len(ls)):
        print('\033[036m',i,ls[i],'\033[0m')  # show steps
        if ls[i]==value:
            return i

l=[0,11,22,33,44,55,66,77,88,99]
print(l)
for i in range(9):
    v=int(input('look up number').strip())
    print(sequential(l,v))

二分查找

# binary search
def binary(ls,value):
    head,tail=0,len(ls)-1
    mid=(head+tail)//2
    while head<=tail:
        if ls[mid]==value:
            return mid
        elif value<ls[mid]:
            print('\033[036m',mid,ls[mid],'\033[0m')  # show steps
            tail=mid-1
            mid=(head+tail)//2
        elif ls[mid]<value:
            print('\033[036m',mid,ls[mid],'\033[0m')  # show steps
            head=mid+1
            mid=(head+tail)//2

l=[0,11,22,33,44,55,66,77,88,99]
print(l)
for i in range(9):
    v=int(input('look up number').strip())
    print(binary(l,v))

字符串查找1

# string find 1
def find1(sentence,word,start=0,end=None):
    if not end:
        end=len(sentence)-len(word)+1
    if end>start and end<=len(sentence)-len(word)+1:
        for i in range(start,end):
            for j in range(len(word)):
                print(i,j,sentence[i+j],word[j],sep='\t')  # show steps
                if sentence[i+j]!=word[j]:
                    break
            else:
                return i

s='To see a world in a grain of sand. And a heaven in wild flower.'
print('find1(s," a ",7)',find1(s,' a ',7))
print('find1(s," a ",7,17)',find1(s,' a ',7,17))
for i in range(9):
    for i in range(len(s)):
        print(i%10,end='')
    print('\033[036m')
    print(s,'\033[0m')
    w=input('word: ')
    n=input('start number: ')
    e=input('end number: ')
    if w and n.isdigit() and e.isdigit():
        print('\033[031m',find1(s,w,int(n),int(e)),'\033[0m')