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#include <iostream>
#include <algorithm>
#include <vector>
#include <string>
#include <unordered_map>
#include <unordered_set>
using namespace std;
class shannonFano{
public:
void afficherTexteOriginal(){
cout << texteACoder;
}
void afficherTexteCode(){
cout << messageCode;
}
void afficherCodesDesCaracteres(){
for(auto car : caracteresPresents){
cout << car << " " << codeDuCaractere[car] << endl;
}
}
shannonFano(string texteACoder):texteACoder(texteACoder){
extraireCaracteresDifferents();
calculerOccurenceDeChaqueCaractere();
trierCaracteresParOccurencesCroissantes();
calculerTableauCumulatif();
calculerLeCodeDeChaqueCaractere();
calculerLeMessageCode();
}
private:
void extraireCaracteresDifferents(){
unordered_set<char> dejaVu;
for(auto caractere : texteACoder)
dejaVu.insert(caractere);
caracteresPresents.insert(caracteresPresents.begin(), dejaVu.begin(), dejaVu.end());
}
void calculerOccurenceDeChaqueCaractere(){
//initialisation a 0 (necessaire?)
for(auto caractere : caracteresPresents)
occurencesDuCaractere[caractere] = 0;
//remplissage
for(auto caractere : texteACoder)
occurencesDuCaractere[caractere] += 1;
}
void trierCaracteresParOccurencesCroissantes(){
sort(caracteresPresents.begin(), caracteresPresents.end(), comparerCaractereParOccurence(this));
}
struct comparerCaractereParOccurence{ //et ordre alphabetique
shannonFano* s;
comparerCaractereParOccurence(shannonFano* s) : s(s){}
bool operator()(const char& a, const char& b){
if(s->occurencesDuCaractere[a] == s->occurencesDuCaractere[b])
return a < b;
else
return s->occurencesDuCaractere[a] < s->occurencesDuCaractere[b];
}
};
void calculerTableauCumulatif(){
int somme(0);
for(auto caractere : caracteresPresents){
somme += occurencesDuCaractere[caractere];
cumulOccurences.push_back(somme);
}
}
void calculerLeCodeDeChaqueCaractere(){
if(caracteresPresents.size() == 1)
codeDuCaractere[caracteresPresents.front()].push_back(CODE_GAUCHE);
else
calculerLeCodeDeChaqueCaractereEntre(0, (int)caracteresPresents.size()-1);
}
void calculerLeCodeDeChaqueCaractereEntre(int debut, int fin){ //fonction recursive
if(fin <= debut) return;
int indexCoupure = separe2PaquetsOccurencesEgales(debut, fin);
//moitie gauche
for(int i = debut; i <= indexCoupure-1; ++i)
codeDuCaractere[caracteresPresents[i]].push_back(CODE_DROITE);
calculerLeCodeDeChaqueCaractereEntre(debut, indexCoupure-1);
//moitie droite
for(int i = indexCoupure; i <= fin; ++i)
codeDuCaractere[caracteresPresents[i]].push_back(CODE_GAUCHE);
calculerLeCodeDeChaqueCaractereEntre(indexCoupure, fin);
}
int separe2PaquetsOccurencesEgales(int debut, int fin){
int offset = (cumulOccurences[debut]-1); //il faudrait trouver un meilleur nom...
int valeurDeSeparation = (cumulOccurences[fin]-offset)/2 + offset;
int indexCoupure = 0;
for(indexCoupure = debut; indexCoupure <= fin; ++indexCoupure){
if(cumulOccurences[indexCoupure] > valeurDeSeparation)
break;
}
return indexCoupure;
}
void calculerLeMessageCode(){
for(auto car : texteACoder){
messageCode.append(codeDuCaractere[car]);
}
}
//var
static char constexpr CODE_GAUCHE ='0';
static char constexpr CODE_DROITE ='1';
string texteACoder;
string messageCode;
vector<char> caracteresPresents;
unordered_map<char, int> occurencesDuCaractere;
unordered_map<char, string> codeDuCaractere;
vector<int> cumulOccurences;
};
int main(int argc, const char * argv[])
{
cout << "Entrez un texte a coder : ";
string texte;
cin >> texte;
shannonFano texteCrypte(texte);
cout << "Le texte : ";
texteCrypte.afficherTexteOriginal();
cout << endl;
cout << "Se code en : ";
texteCrypte.afficherTexteCode();
cout << endl;
cout << "Avec les clefs suivantes : \n";
texteCrypte.afficherCodesDesCaracteres();
cout << endl;
return 0;
} |
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