C++ issue with LZW decoding - c++

Question

I'm writing a LZW algorithm and I'm having trouble with decoding the encoded file. The encoding function works fine,the issues is as far as I know in the building of the dictionary in the decoding function.
Edit: The size of the decoding dictionary is for 1 bigger than the encoding dictionary. Also the decoding dictionary doesn't seem to contain any string value that has more than 2 characters. For testing I used a .txt file of Alice in wonderland and the first few words are ok but after that everything goes wrong
My encoding function:
void encode(char* path, int vel_s){
unordered_map<string,int>dict; //dictionary
int bit_size = ceil(log2(vel_s + 1)); //size of codes - x bits
//init dictionary
for(int i = 0; i < 256; i++){
string k = "";
k.push_back((unsigned char)i);
dict[k] = i;
}
int count = 256, maxVel = pow(2, bit_size); //counter and max value in bits
BinReader reader(path);//text to encodede
BinWriter writer("out.bin");//output file
string P = "";
P.push_back(reader.readByte());//read first char
while(!reader.f.eof()){
char C = reader.readByte(); //read next char
if(dict.find(P + C) != dict.end()){ //if in dictionary
P+=C;
}else{ //if not in dictionary
if(count >= maxVel){
count = 0;
}
int out = dict[P]; //int code of P
string binString = toBinary(out, bit_size); //binary value of out
for(int i = 0; i<binString.size();i++){ //write bits
if(binString[i]=='1'){
writer.writeBit(true);
}else{
writer.writeBit(false);
}
}
dict[P + C] = count; //write P+C to dictionary
count++;
P = C; //overwrite P
}
}
//write last output
int out = dict[P];
string binString = toBinary(out, bit_size);
for(int i = 0; i<binString.size();i++){
if(binString[i]=='1'){
writer.writeBit(true);
}else{
writer.writeBit(false);
}
}
}
And this is the decoding function:
void decompress(char* path, int vel_s){//file path + dictionary max size
unordered_map<int,string>dict; //dictionary
int bit_size = ceil(log2(vel_s + 1));//max number of bits in code
for(int i = 0; i < 256; i++){ //init dictionary
dict[i] = (unsigned char) i;
}
int count = 256; //counter
vector<bool>B;
BinWriter writer("out_d.txt"); //output file
BinReader reader(path); //input file
int newI, oldI; //new and old value
for(int i = 0; i < bit_size; i++){ //read code from encoded file of size bit_size
B.push_back(reader.readBit());
}
oldI = convertToInt(B); //convert to integer
string S = dict[oldI]; //String is dictionary value of old value
writer.writeByte(S[0]); //write first letter
string C = ""; //init C
C =S[0]; //C is first character of S
int maxVel = pow(2, bit_size); //max value of encoded code
while(!reader.f.eof()){
B.clear();//clear vector B for reading bits
for(int i = 0; i < bit_size; i++){
B.push_back(reader.readBit());//read next code
}
newI = convertToInt(B); //convert bits to int
if(dict.find(newI) == dict.end()){ //if new value not in dictionary
S = dict[oldI]; //S is value of old code
S += C; //concat C to S
}else{
S = dict[newI]; //S is value of new code
}
for(int k = 0; k < S.size(); k++){ //write S to file
writer.writeByte(S[k]);
}
C = "";
C += S[0]; //C is first character of S
dict[count] = dict[oldI] + C; //new input in dictionary
count++;
oldI = newI; //old value is new value
}
And the toBinary() and convertToInt() functions that I use for help
string toBinary(int x, int l){
string temp;
while(x!=0){
temp =(x%2==0 ? "0":"1")+temp;
x/=2;
}
while(temp.length() != l){
temp = "0"+temp;
}
return temp;
}
int convertToInt(vector<bool>B){
int power= B.size()-1,res= 0;
for(int i = 0; i < B.size(); i++){
if(B[i]){
res+=pow(2, power);
}
power--;
}
return res;
}