(edit because of formatting issues. How do you use newline in cf posts anyway?) ``

I have some beginner friends and people asking me how to do multi-testcase format and how to use fast I/O for different languages so I suppose I will just put it here for newbies-and-unrated-people-who-aren't-familiar-to-this-yet's reference. Apparently it's more of not understanding how multi-testcase / fast IO works rather than not knowing how to code it. It's a lot easier to explain using code.

C++ 17 (also known as the Andersons' format):

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

void solve(){
//insert code here
}

signed main (void){
    int N; cin >> N;
    for (int l=0; l < N; l++){
        solve();
    }
}

Fast I/O

#inlcude <bits/stdc++.h>
using namespace std;
void fastscan([your type] &number){
    bool negative = false;
    register [your type] c;
    number = 0;
    c = _getchar_nolock();
    if (c=='-'){
        negative = true;
        c = _getchar_nolock();
    }
    for (; (c>47 && c<58); c=_getchar_nolock())
        number = number *10 + c &mdash; 48;
    if (negative)
        number *= -1;
}

signed main (void){
    ios_base::sync_with_stdio(false);
    cin.tie(NULL);
    int N; cin >> N;
    for (int l=0; l < N; l++){
        solve();
    }
}

Note that this may vary, I used geany _getchar_nolock. The more recognized version should be getchar_unlocked.

Kotlin:

fun main() {
    val br = System.`in`.bufferedReader()
    val pw = System.out.bufferedWriter() //these two lines are the fast output/inputs

    val n = br.readLine().toInt() //the umber of testcases are usually in one line
    repeat(times = n){
        //insert code here
    }
    pw.flush()
}

Python: (one of my less used languages and thus I don't know much about it's fast I/O)

def solve():
    #insert code

t = int(input().strip())
for _ in range(t):
    solve() 

I am probably one of the less qualified people to teach you guys but I'll be glad if this helps :D I'm quite interested in how this will work for js since when I prompted deepseek it gave a very long and weird response. I will appreciate it if someone can explain in the comments.