Thread: Question on permutated indices

I'm doing an example from the book which I have to create a permuted permute the index, the book says it takes a sentence (in this case two), ad this is the in/output

Code:

 
The quick brown fox
jumped over the fence

[b]output[b]
      The quick   brown fox
jumped over the   fence
the quick brown   fox
                  jumped over the fence

etc..

The algorithm in the book suggests I do two things which i have, which is extract the sentence and then make rotations, I did so with these functions

Code:

#include "functions.h"
#include <cctype>
#include <sstream>

using std::vector;
using std::string;
using std::istringstream;

typedef vector<string>::size_type str_sz;

vector<string> parse(const string& aStr)
{
    istringstream words(aStr);
    string temp;
    vector<string> parsed;
    
    while(words >> temp)
        parsed.push_back(temp);
               
    return parsed;
}

vector<string> rotations (const string& aStr)
{
    
    vector<string> parsed = parse(aStr);
    str_sz words = parsed.size();
    
    vector<string> permutations;    
    string final, first, temp;
    
    permutations.push_back(aStr); //puts the first string from the start
    temp = aStr;
    
    //does nubmer of rotations as there are words(excluding  one for first sentence)
    for(str_sz i = 0; i < words - 1; i++)  
    {
        istringstream body(temp); //sets the sstream object to the temp string
        
        body >> first;   //holds the first word of the sstream
        
        while(body >> temp)
            final += temp + " ";  //concatenates the rest of the sstream
        
        final += first;  //puts the first word at the end
        
        permutations.push_back(final);  //puts that rotation into 
        
        temp = final;    //sets temp
        final = "";  
    }  
    return permutations; 
}

The first function just parses the words, I use that for the sake of getting the number of words so I can do a certain number of rotations. Now the second function gets the string into a istringstream and then gets the first word into a string variable, and the rest into another string variable, the concatenates the body with the first word to create one rotation and puts that into an array. It then creates a new istringstream with the string value of the last rotation. It works fine.

the next thing is to sort the rotations, which I assume is already done since I pushed them back in the array in the order I rotated them

then this is where I'm confused...it says I should "unrotate and write the permuted index, which involves finding the separator, putting the phrase back together, and writing it propperly formatted"

Maybe it's because I'm not familiar with what a permuted index is (though I understand the concept of permutations), that I'm having trouble with this. If someone could re-word it so I can wrap my head around what I am to do, it would be helpful.