How to Reverse a given sentence (string) in C++? - c++

Question

Example: if the input was DOGS LIKE CATS
output- CATS LIKE DOGS
consider that I have to use only : If-else conditions, while & for loops, Arrays, strings and Functions. NOT strings functions, Pointers & Dynamic memory allocation & structures.
Spaces need to be the same as the example as well.
I tried to do the following but it doesnt work can you help please?
void revSent(char str[]){
char temp[100];
int k;
for (i=sentenceSize ; i>0 ; i--)
for (k=0 ; k<sentenceSize ; k++)
temp[k]=str[i];
for (k=0 ; k<sentenceSize ; k++)
if (temp[k]!=' ')
for (i=k ; i>0 ; i--)
printf("%c", temp[i]);
}

Answer 1

It's easy to do this in-place, without any additional data structures:
reverse the whole string: DOGS LIKE CATS -> STAC EKIL SGOD
reverse each word in the string: STAC EKIL SGOD -> CATS LIKE
DOGS
Hint: you can use the same function for both (1) and (2).

Answer 2

You could implement the following to arrive at a solution:
Separate the sentence into a list of words.
Reverse this list.
Concat this list together to form the sentence.

Answer 3

If you define a word as a whitespace-delimited token then the following will do:
std::vector<std::string> sentence;
std::copy(std::istream_iterator<std::string>(std::cin),
std::istream_iterator<std::string>(),
std::back_inserter(sentence));
std::reverse(sentence.begin(), sentence.end());
In essence you want to start with the definition of a word, then place in a container your words, and finally use std::reverse() to reverse them.
For an algorithms homework your instructor probably won't be satisfied with this. You want to create a function that splits a sentence into words. You can, of course, work with pointers within the same string -- and that may well be the intent of your instructor, but if that isn't what you must then I personally find working with a container easier.

Answer 4

I'll give a hint: since you can't use data structures you can't directly use Paul or OJ's method. BUT, recursive function calling would form a stack.

Answer 5

Break the sentence into words
In order, push each word onto a stack
Pop each item off the stack and print out/add to list/write to file/whatever.
Voila!

Answer 6

who says the STL isn't useful?
Depending on how you do this, there are different ways to attack this.
my way is just:
while (original_string isn't empty){
take first word
prepend to reversed string
}
Here's the C++ solution (using find and substr, two very useful string functions)
using namespace std;
string word_reverse(string original){
string reverse_string;
if (original.find(' ')!=string::npos){
do{
int pos=original.find(' ');
//prepend word
reverse_string=original.substr(0,pos)+' '+reverse_string;
//remove word from original,considering the found whitespace
original=original.substr(pos+1,original.length()-(pos+1));
}while(original.find(' ')!=string::npos);
//don't forget the last word!
return original+' '+reverse_string;
}
else{//no whitespace: return original text
return original;
}
}