input / output

Always MUST add :~ ios_base::sync_with_stdio(false);

caution

MUST ADD 👇

    ios::sync_with_stdio(false);
    // ios_base::sync_with_stdio(false);  // used by "ksun48" & "ecnerwala"

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MUST Add :~ cin.tie(NULL);

caution

    cin.tie(nullptr);   // used by ""ksun48" "2021 CodeJam Champion" & "ecnerwala"
    // cin.tie(NULL);
    // cin.tie(0);  // used by "TOURIST" & "maroonrk"

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Using scanf & printf

// #include <bits/stdc++.h>
#include <vector>
#include <iostream>
#include <climits>
#include <algorithm>
// #include <array>
//#include <string>

using namespace std;

int main()
{
    //FASTER THAN cout and cin
    //printf and scanf from C
    int n, key;
    scanf("%d %d", &n, &key);

    printf("%d  %d   %d\n%d %d", n, key, key, key, n); //the way "%d %d" is written determines the way Output is printed
                                                       //the the no. of times "%d" is equal to the no.s of variables

    //cin and cout from C++
    int a, keys;
    cin >> a >> keys;

    cout << a << " " << keys << "\n"; //"\n" should be used instead of endl

    string str;
    getline(cin, str); //to take a whole line as input "getline(sin, variable_name) is used"

    return 0;
}

OPTIONAL

flush

caution

Try to flush as little as possible.

But always flush where necessary.

cout << flush;

OR

cout.flush();

OR

cout << endl;

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