Help me in solving GSCV209 problem

My issue

why we write t-- inside the while loop

My code

// Solution as follows

#include <bits/stdc++.h>
using namespace std;

int main() 
 int t;
 //accept the count of test cases given in the the 1st line
 //Run a loop to accept 't' inputs
   int N;
 //accept an integer N in each test case
 //output the number mirror for each test case
 return 0;

Learning course: C++ for problem solving - 1
Problem Link: CodeChef: Practical coding for everyone

TLDR: This is the shortest way to loop through all the test cases.

Basically we want to loop from 1 till t so that we can handle each test. To do that we can either write a for loop like this

for (int i = 1; i <= t; i++) {


But for loop needs this much code, so we use while loop. With while loop you can write a condition like

while (t>0) {
  // Do stuff
  t = t-1;

We can then compress it more by just using while(t--) which will stop when t becomes zero.

This is best way to decrement the loop index and will stop when t becomes zero using while(t–).

otherwise we will do the decrement inside the loop

while (t>0) {
// statements