binexp.cpp

// UNCOMMENT THE NEXT LINE TO ENABLE THE TESTS AND BEFORE SUBMITTING
//#include "tests.h"

#include <iostream>
using namespace std;

// PRE 0<= x < 2
// POST: return value is the binary representation of the inputed variable with 16 significant bits
void binExp(double dec);
int main(){
    double d;
    cin >> d;
    if(d >= 0 && d < 2) binExp(d);
    else cout << "not allowed";
    return 0;
}
void binExp(double dec){
    for(int i = 0; i < 16; i++){
        if(dec>=1){
            cout << 1;
            dec -= 1;
            dec *= 2;
        } 
        else{
            cout << 0;
            dec *= 2;
        } 
        if(i==0) cout << ".";
    }
}

linetest.cpp

// UNCOMMENT THE NEXT LINE TO ENABLE THE TESTS AND BEFORE SUBMITTING
#include "tests.h"

#include <iostream>
#include <cmath>
using namespace std;
double calcFunc(double x){
    return 0.9*x + 0.7;
}
double precision(double x){
    //if(nextafter(x,0)>nexttoward(x,0)) return nextafter(x,0)-x; // too exact
    //else return x-nexttoward(x,0);    // ungefähre abschätzung http://de.cppreference.com/w/cpp/numeric/math/nextafter
    return x * 1e-5; // to upper one is probably more exact than the one in the tests.h
}
void checkOnG(double a,double b, double p){
    if( a - b < p) cout << "yes";
    else cout << "no";
}

int main(){
    double x,y,p;
    cin >> x >> y;
    p = precision(x);
    if(y-calcFunc(x) > 0){ // y is bigger than the function
        checkOnG(y,calcFunc(x),p);
    }
    else if(y-calcFunc(x) < 0){ // y is smaller than f | we need this because we are not allowed to use abs
        checkOnG(calcFunc(x),y,p);
    }
    else{ // point is on g exactly, even in binary represention
        cout << "yes";
    }
    return 0;
}

round.cpp

// UNCOMMENT THE NEXT LINE TO ENABLE THE TESTS AND BEFORE SUBMITTING
//#include "tests.h"
#include <iostream>
using namespace std;
// PRE: x is roundable to a number
//      in the value range of type int
// POST: return value is the integer
//       nearest to x, or the one closer
//       to 0 if x lies right in between
//       two integers.
int round(double x);
int main(){
    double a;
    cin >> a;
    cout << round(a);
}

int round(double x){
    double tmp;
    tmp = x;
    tmp += 0.5 - x;
    if( x <= 0){ //0.0 - 0.5
        return x;
    }
    else{ //0.51 - 0.999
        return x + 1;
    }
}