Question

I read of a job interview question to write some code for the following:

Write an efficient function to find the first nonrepeated character in
a string. For instance, the first nonrepeated character in “total” is
‘o’ and the first nonrepeated character in “teeter” is ‘r’. Discuss
the efficiency of your algorithm.

I came up with this solution in Python; but, I’m sure that there are way more beautiful ways of doing it.

word="googlethis"
dici={}

#build up dici with counts of characters
for a in word:
    try:
        if dici[a]:
            dici[a]+=1
    except:
        dici[a]=1

# build up dict singles for characters that just count 1 

singles={}
for i in dici:
    if dici[i]==1:
        singles[i]=word.index(i)

#get the minimum value

mini=min(singles.values())

#find out the character again iterating...

for zu,ui in singles.items():
    if ui==mini:
        print zu 

Is there a more concise and efficient answer?

Answer 1

In [1033]: def firstNonRep(word):
   ......:     c = collections.Counter(word)
   ......:     for char in word:
   ......:         if c[char] == 1:
   ......:             return char
   ......:         

In [1034]: word="googlethis"

In [1035]: firstNonRep(word)
Out[1035]: 'l'

EDIT: If you want to implement the same thing without using helpers like Counter:

def firstNonRep(word):
    count = {}
    for c in word:
        if c not in count:
            count[c] = 0
        count[c] += 1
    for c in word:
        if count[c] == 1:
            return c