not reading the first line [on hold]

I was using the following code to read information from a file (b.txt) into a vector. every time I execute, the program starts reading from the second line. So vector_b[0] = the second line instead of the first line.

I'm still not used to c++ hope you can help

string line_b;
int idx = -1;
float *vector_b = new float[1];
float element_b;
if (file_b.is_open() && file_b.good()) {
    cout << "File is open. \n";
    while (getline(file_b, line_b)) {
        stringstream stream_b(line_b);
        while(1) {
            stream_b >> element_b;
            if(!stream_b) {
                break; }
            idx = idx+1;
            float *tempArr = new float [idx];
            copy(vector_b, vector_b + idx, tempArr);
            tempArr[idx] = element_b;
            delete [] vector_b;
            vector_b = tempArr;
        }
    }        
    } 
    else {
        cout << "Failed to open file.";
    }