Srm144BinaryCodeHerb

Srm144300.cxx

#include<vector>
#include<iostream>
using namespace std;

class BinaryCode {
private:
  char decodeChar(const string& message, const string& decoded, int pos){
    if(pos == 1) return  (getIntFromChar(message[pos-1]) - getIntFromChar(decoded[pos-1]) + '0');
    return (getIntFromChar(message[pos-1]) - getIntFromChar(decoded[pos-2]) - getIntFromChar(decoded[pos-1]) + '0');
  }
  int getIntFromChar(const char c){
    return (c - '0');
  }
public:
  vector<string> decode(const string& message){   
    vector<string> rVector;
    rVector.push_back("NONE");
    rVector.push_back("NONE"); 
    //special case
    if(message.length() == 1){
      if(message[0] == '0')
	rVector[0] = "0";
      else if(message[0] == '1')
	rVector[1] = "1";
      return rVector;
    }
    // loop twice - once for p[0] = 0 and then for p[0] =1
    for(int i = 0; i < 2; i++) {
      string rString = "";
      rString.push_back(i + '0'); 
      int j = 1;
      for(; j < message.length(); j++){
	char cZero = decodeChar(message, rString, j);
	if(cZero != '0' && cZero != '1') 
	  break;
	else
	  rString.push_back(cZero);
      }
      // sanity check
      if(j == message.length())
	if(getIntFromChar(message[message.length()-1]) == getIntFromChar(rString[rString.length()-1]) + getIntFromChar(rString[rString.length()-2]) )
	  rVector[i] = rString;
    }
    return rVector;  
  }  
};