How to find a duplicate in a list without in-built functions in Python?

Question

I'm trying to find if there is a duplicate within a list without using the in-built functions. So far I have something like this however it does not seem to be working. Can anyone help? Give pointers? Improvements? I'd appreciate it. (Python version 2.7.10)

def DupSearch(list):
counter=0
for i in range(len(list)):
    if list[i]==list[0]:
        for j in range(len(list)):
            if list[j]!=list[j+i]:
                print "No duplicated"
            else:
                counter=counter+1
                if counter == len(list):
                    print "Duplicate found"

DupSearch([1,2,3,4,5,3])

len() and range() are built-in functions. Can we use set()? — Ahasanul Haque
– Ahasanul Haque, Commented Oct 25, 2015 at 21:19
I'm not entirely sure. Would it be more difficult without set()?. Otherwise it'd simply be if len(list)!=len(set(list)): print True. else: print False? — Sectah
– Sectah, Commented Oct 25, 2015 at 21:21

uselpa · Accepted Answer · 2015-10-25 21:28:42Z

1

Something like this?

def DupSearch(list):
    for i in range(len(list)):
        for j in range(i+1, len(list)):
            if list[i]==list[j]:
                print "Duplicate found"
                return
    print "No duplicated"

answered Oct 25, 2015 at 21:28

uselpa

19k2 gold badges36 silver badges53 bronze badges

Sign up to request clarification or add additional context in comments.

1 Comment

Sectah Over a year ago

I really overcomplicated this. Thank you so much.

Ahasanul Haque · Accepted Answer · 2015-10-25 21:28:52Z

0

You can use a dictionary to store the frequency of individual element,

lst=[1,3,5,7,6]
dic={}

for i in lst:
    if i in dic.keys():
        dic[i]+=1
    else:
        dic[i]=1


duplicate= False

for key,value in dic.iteritems():
    if value>1:
        duplicate = True
        print "List has duplicate element"
        break

if not duplicate:
    print "No duplicate element"

answered Oct 25, 2015 at 21:28

Ahasanul Haque

11.2k6 gold badges45 silver badges61 bronze badges

Collectives™ on Stack Overflow

How to find a duplicate in a list without in-built functions in Python?

2 Answers 2

1 Comment

Comments

Your Answer

Hot Network Questions

Collectives™ on Stack Overflow

2 Answers 2

1 Comment

Comments

Your Answer

Sign up or log in

Post as a guest

Related