Help me in solving LOOP6V2 problem

Problem Link: CodeChef: Practical coding for everyone
Learning course: Learn C++

My code

#include <bits/stdc++.h>
using namespace std;
int main() {

    int num;
    int fact = 1;
    cin >> num;
    for(int a = num; a >= 2; a = a--)
        fact = fact * a;
    cout << "The factorial of the given number is: " << fact << endl;

    return 0;

My issue

why time limit excedded in this way and not in (–a) in the for loop i think the are same in this condition’

using namespace std;
int main(){
    int num;
    int x=1;
    int y=1;
    cout<<"The factorial of "<<num<<" is :"<<y;
    return 0;

When you do a = a--, what happens is that a is decremented by 1, but the previous value is still assigned to the new variable. So in effect the value of a is never changing in this loop.

For a = --a, here also the value is decremented by 1 and the new value is assigned to a. Thus a keeps decreasing.

An easy way to understand this is by using two different variables. Run these two codes by yourself to see.

int a = 2;
int b = a--;
cout<<b<<'\n'; // b will be 2
int a = 2;
int b = --a;
cout<<b<<'\n'; // b will be 1