Redefinition error when trying to move class to a separate file - c++

Question

I am trying to implement a class in c++ but I keep getting an error.
My .cpp looks like:
#include "medianfinderheader.h"
MedianFinder::MedianFinder() {
}
void MedianFinder::addNum(int num) {
}
double MedianFinder::findMedian() {
double x=1.0;
return x;
}
while my header file looks like:
class MedianFinder {
public:
MedianFinder() {};
void addNum(int num) {};
double findMedian() {
double x=1.0;
return x;
};
};
However I keep getting the following error :
g++ -I./ -g -Og -std=c++14 main.cpp MedianFinderClass.cpp -o medianEX
MedianFinderClass.cpp:2:5: error: redefinition of 'MedianFinder::MedianFinder()'
2 | MedianFinder::MedianFinder() {
| ^~~~~~~~~~~~
In file included from MedianFinderClass.cpp:1:
medianfinderheader.h:3:5: note: 'MedianFinder::MedianFinder()' previously defined here
3 | MedianFinder() {};
| ^~~~~~~~~~~~
MedianFinderClass.cpp:5:10: error: redefinition of 'void MedianFinder::addNum(int)'
5 | void MedianFinder::addNum(int num) {
| ^~~~~~~~~~~~
In file included from MedianFinderClass.cpp:1:
medianfinderheader.h:4:10: note: 'void MedianFinder::addNum(int)' previously defined here
4 | void addNum(int num) {};
| ^~~~~~
MedianFinderClass.cpp:9:12: error: redefinition of 'double MedianFinder::findMedian()'
9 | double MedianFinder::findMedian() {
| ^~~~~~~~~~~~
In file included from MedianFinderClass.cpp:1:
medianfinderheader.h:6:12: note: 'double MedianFinder::findMedian()' previously defined here
6 | double findMedian() {
I have no idea why this is happening when I've implmented classes like this before any help would be appreciated.
I have implemented classes in c++ in this exact same way, and I'm just really frustrated any help would be greatly appreciated.

Answer 1

this line
void addNum(int num) {};
creates an implementation of addNum with an empty body, you need
void addNum(int num);
same for other functions in that class