decrypt.cpp

#include <vector>
#include <string>
#include <cstdio>
#include <algorithm>
#include <cstring>
using namespace std;
main()
{
    vector < vector <int> > judge;
    string sample=". abcdefghijklmnopqrstuvwxyz";
    string teststr="the quick brown fox jumps over the lazy dog.";
    int testlen=teststr.length();
    vector <int> ans;
    //a vector of characters which have already been matched.
    vector <char> matchedchars;
    
    //creating our judge
    for (int i=0;i<sample.length();i++)
    {
        ans.clear();
        for (int j=0;j<teststr.length();j++)
        {
           if (teststr[j]==sample[i])
            ans.push_back(j);
        }
        judge.push_back(ans);
    }
    
    //printing the judge to ensure its correct
    /*
    for(int i=0;i<judge.size();i++)
    {	
        printf("%c ",sample[i]);
        for(int j=0;j<judge[i].size();j++)
        {
            printf("%d ",judge[i][j]);
        }
        printf("\n");
    }
    */
        
    //Here para is the string where the paragraph is kept.
    string para="the quick brown fox jumps over the lazy dog.";
    
    //si is the startindex of the string variable with the entire paragraph
    for(int si=0;si<=para.length()-testlen;si++)
    {
        int condition=1;
        //ji is the judge index
        int ji=0;
        matchedchars.clear();
	
        //we run aour entire judge, and stop if any unwanted condition:
        //a character mismatch in position
        //or an unwanted repitition
        while(condition and ji<judge.size())
        {
            int match=0;
            for(int i=0;i<judge[ji].size();i++)
            {
            //tolower used to eliminate case sensitivity issues.
                if(tolower(para[si+judge[ji][i]])==tolower(para[si+judge[ji][0]]))
                    match++;
            }
            if(match!=judge[ji].size() or find(matchedchars.begin(), matchedchars.end(), para[si+judge[ji][0]])!=matchedchars.end())
            {
                condition=0;
                break;
            }
            matchedchars.push_back(para[si+judge[ji][0]]);
            ji++;
        }
	
        if(condition and ji==judge.size())//we have found the key.
        {
            //constructing the QMap and break
            for(int i=0;i<teststr.length();i++)
            {
                // character para[si+i] is mapped to character teststr[i]
            }
            break;
        }
    }
}