In the previous post I wrote about reversing a word or an input string. In this one, let’s look at reversing a sentence. For example: “landed has Eagle The” should become “The Eagle has landed”.
To achieve this we’re going to build on top of the string reversal code from the previous post.
def reverse_word(word):
letters = list(word)
start = 0
end = len(letters)-1
while start < end:
letters[start], letters[end] = letters[end], letters[start]
start+=1
end-=1
return ''.join(letters)
def reverse_sentence(words):
# reverse the whole string -- # O(n)
words = reverse_word(words)
# convert string to a list
temp = words.split(' ')
# reverse each word in that list -- # O(n)
for i in range(len(temp)):
temp[i] = reverse_word(temp[i])
# the above loop is O(n)
# because we only go through every letter once
# convert list to a string and return it
return ' '.join(temp)
reverse_sentence('landed has Eagle The') #Output: The Eagle has landed
In the code above, we accept an input string, use the string reversal function to reverse it. This gets us ehT elgaE sah dednal as the output and we store it in temp by splitting it at spaces.
The next step is to use string reversal code again but this time we use it for each word and that gets us our intended output, which is: The Eagle has landed.
CS Mumbai 