how to find words in a sentence that have even reverse of those words in python

Question

I would like to get find all the words that have reversed words in a same sentence. How ever, the code I got finds only first occurrence of the word. in my sentence "i am going to eat ma and tae will also go", I should get an output of am( ma is reversed word) and eat( tae is the reversed word). I only get am..how can i modify this code to get all the words that have reversed words in it i.e. both am and eat.

input_str='i am going to eat ma and tae will also go'
word=input_str.split()
def isReverseEqual(s1, s2): 

    # If both the strings differ in length 
    if len(s1) != len(s2): 
        return False

    l = len(s1) 

    for i in range(l): 

        # In case of any character mismatch 
        if s1[i] != s2[l-i-1]: 
            return False
    return True
def getWord(str, n): 
    reverse=[]
    # Check every string 
    for i in range(n-1): 

        # Pair with every other string 
        # appearing after the current string 
        for j in range(i+1, n): 

            # If first string is equal to the 
            # reverse of the second string 
            if (isReverseEqual(str[i], str[j])): 
                reverse.append(str[i])
                return reverse 


    # No such string exists 
    return "-1"
print(getWord(word, len(word)))

Output: ['am','eat'] is what expected.

In my opinion this activity technically cannot be done 100% correctly. what happen If you enter word "deal" but you really want word "lead". — Kalana
– Kalana, Commented Mar 11, 2020 at 7:51
you are expecting ['am','eat'] and not ['ma', 'tea'] because am and eat appears first in the sentence? or it doesn't matter the order of the expected output? — kederrac
– kederrac, Commented Mar 11, 2020 at 8:12

kederrac · Accepted Answer · 2020-03-11 07:53:39Z

3

you can use:

words = input_str.split()

s = set()
result = set()
for w in words:
    r = w[::-1]
    if r in s:
        result.add(r)
    else:
        s.add(w)

list(result)

output:

['am', 'eat']

this is O(n) time complexity solution, so you have to get first the words and iterate through them, each time you have a new word you are adding him to a set, if the reverse is already in the set you are adding the reverse to the result

edited Mar 11, 2020 at 7:53

answered Mar 11, 2020 at 7:45

kederrac

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Comments

Kami · Accepted Answer · 2020-03-11 07:52:14Z

just change the indent of line "return reverse" :

input_str='i am going to eat ma and tae will also go'
word=input_str.split()
def isReverseEqual(s1, s2):

    # If both the strings differ in length
    if len(s1) != len(s2):
        return False

    l = len(s1)

    for i in range(l):

        # In case of any character mismatch
        if s1[i] != s2[l-i-1]:
            return False
    return True
def getWord(str, n):
    reverse=[]
    # Check every string
    for i in range(n-1):

        # Pair with every other string
        # appearing after the current string
        for j in range(i+1, n):

            # If first string is equal to the
            # reverse of the second string
            if (isReverseEqual(str[i], str[j])):
                reverse.append(str[i])
    if reverse:
        return reverse
    else:    # No such string exists
        return "-1"
print(getWord(word, len(word)))

Zaraki Kenpachi · Accepted Answer · 2020-03-11 07:47:46Z

0

input_str= 'i am going to eat ma and tae will also go'
words_list = input_str.split()
new_words_list = [word[::-1] for word in words_list]

data = []
for i in words_list:
    if len(i) > 1 and i in new_words_list:
        data.append(i)

Output:

['am', 'eat', 'ma', 'tae']

answered Mar 11, 2020 at 7:47

Zaraki Kenpachi

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Comments

DYZ · Accepted Answer · 2020-03-11 07:52:00Z

0

Your solution is overcomplicated. For example, function isReverseEqual can be written in one line:

def isReverseEqual(s1, s2):
    return s1==s2[::-1]

Let's simplify it. First, treat your sentence as a set, not a list, because set lookups are more efficient:

words = set(input_str.split())

Next, select the words from the set/list if their reversed copy is also in the set/list and they are alphabetically smaller than the reversed copy (to avoid duplicates):

[w for w in words if w[::-1] in words and w < w[::-1]]
#['am', 'eat']

This solution works for lists, too.

answered Mar 11, 2020 at 7:52

DYZ

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