Prefix and Postfix Increment and Decrement of C++, Java, and C#

Question

Why is the output of C++ -1, while Java and C# will output 0?

#C++
#include <iostream>
using namespace std;

int main() {
int x = 6;
x = (++x) - (x--);
cout << x << endl;
return 0;
}

#Java
public class Program
{
public static void main(String[] args) {
int x = 6;
x = (++x) - (x--);
System.out.println(x);
}
}

#C#
using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;

namespace SoloLearn
{
class Program
{
static void Main(string[] args)
{
int x = 6;
x = (++x) - (x--);
Console.WriteLine(x);
}
}
}

Answer 1

It's to do with sequencing / sequence points.
https://en.m.wikipedia.org/wiki/Sequence_point

Answer 2

https://stackoverflow.com/questions/949433/why-are-these-constructs-using-pre-and-post-increment-undefined-behavior